sample trb 5r - nelson

AUTHORSBarry LeDrew

Jim Axford

Allan Carmichael

Doug Fraser

Karen Morley

John Munro

Darrell Scodellaro

PROGRAM CONSULTANTBarry LeDrew

Teacher’s Resource

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Contents iiiNEL

Contents

Lesson Plans

Chapter 10: Radioactivity and the Atom

10.1 Radioactivity and its History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

10.2 Radioactivity and the Nucleus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

10.3 Radioactive Decay. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Investigation 10A Penetrating Ability of Nuclear Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

10.4 Half-Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Investigation 10B The Half-Life of Popcorn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Chapter 10 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Chapter 10 Blackline Masters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

BLM 10.3-1 Alpha, Beta and Gamma Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

BLM 10.3-2 Writing Nuclear Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

BLM 10.4-1 Radioactive Decay and Half-Life. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

BLM 10.4-2 Radioactivity Concept Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Chapter 10: Blackline Masters and Worksheets Answer Key. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

UNIT

C Radioactivity

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Chapter 10 Radioactivity and the Atom 1NEL

10CHAPTER

Radioactivity and the Atom Page 274

Key Ideas Vocabulary

Atoms of a single element that differ in massare called isotopes.

There are three basic types of radioactivedecay and these processes can be written asnuclear equations.

The rate of decay of a radioactive sample ispredictable and is described by the half-life ofthe radioactive isotope.

radioactivitynucleusprotonneutronisotoperadioactive decayparent nucleus

daughter nucleusalpha particle (�)beta particle (�)gamma ray (�)half-lifedecay series

TEACHING NOTES

• Possible Misconceptions– Identify: Students may think that radiation is something given off by a few

dangerous materials confined to scientific or medical laboratories ornuclear power plants.

– Clarify: Explain to students that living things are exposed constantly tobackground radiation from both natural and human-made sources. Pointout that radioactive isotopes exist throughout nature in rocks, soils, water,plants, and even in our own bodies. Human-made sources of backgroundradiation include televisions, computers, and some medical equipment.Remind students that low levels of natural background radiation aregenerally not harmful.

– Ask What They Think Now: Ask, How has your understanding of the sourcesof radiation changed?

• To gauge prior knowledge, ask students where they have heard or seenreferences to radiation or radioactivity before. For most students, radiationand radioactivity have negative connotations. Tell them to keep note ofif/how their perceptions change as they study this chapter.

• Many people have concerns about exposure to radiation from nuclear powerplants, especially after the well-publicized incidences at Three Mile Islandand Chernobyl. High doses of radiation or prolonged exposure can bedangerous to humans and other living things. Reassure students, however,that the background radiation to which humans are exposed is generally notat a harmful level. Point out that, overall, nuclear power plants have excellentsafety records.

• Carry out with students Try This: Radioactivity All Around Us.

• Information is available on the Nelson Science website wherever a Go iconappears in the Student Book.

Related Resources

B.C. Probe 10

Computerized

Assessment Bank

B.C. Science Probe 10

Create and Present:

Modifiable Presentations

and Illustrations CD

Thomson Gale Science

Resource Center

Nelson Science Probe 10

Website

www.science.nelson.com

Technology ConnectionsExplain to students that

many countries rely on

nuclear power for

generation of electricity.

Point out that in 2002,

nuclear power provided

13 % of Canada’s

electricity.

The atoms of some elements are radioactive,which means that they undergo radioactivedecay.

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NEL2 Unit C: Radioactivity

• Multimedia activities are available on the Nelson Science website whenever agreen Multimedia icon appears in the Student Book.

• As you progress through the chapter, prompt students to make study notesin the Study Guides found in the Student Workbook.

TRY THIS: RADIOACTIVITY ALL AROUND US

Purpose• Students examine everyday sources of radiation.

Notes• Materials: Geiger counter, glass crystal, pottery glaze, smoke detector, wristwatch

• Assign a student volunteer to be the timekeeper for the demonstration.

• Note that the wristwatch used should be an analog type watch with a glowing hand. These glowing hands are

painted with tritium. A digital watch or an analog watch without a glowing hand will not produce detectable

radiation.

Suggested Answers

A. The smoke detector had the highest number of counts per minute. The glass had the lowest.

B. It would be more accurate to record the number of counts per hour and divide to get the number of counts per

minute. Averages are generally more accurate with a larger sample size. However, extrapolating from number

of counts per minute is probably a reasonable method.

ESL

• Have students create idea webs in response to the question about where or what they have heard aboutradiation and radioactivity. Allow them to use sketches, single words, or simple phrases in their webs. Tellthem to keep their idea webs so they can revise them with more sketches, words, or phrases at the end ofthe chapter.

Extra Support

• Provide guidance for the Try This activity. Have them write Many counts, more radiation and Few counts, lessradiation above their data tables as a reminder. To reinforce the take-home message of the activity forstudents, ask them to make a conclusion about whether humans can avoid all radiation. (no; There isalways some background radiation. Many everyday objects give off radiation.)

Extra Challenge

• Have students work in small groups to research the nuclear power plant incident that occurred at ThreeMile Island in March 1979 or in Chernobyl in April 1986. Have them act in the role of newspaperreporters to produce brief news accounts describing what happened.

Meeting Individual Needs


Radioactivity and its History Page 275


10.1

PRESCRIBED LEARNING OUTCOMES

• explain radioactivity using modern atomic theory• demonstrate scientific literacy • describe the relationship between scientific principles and technology

KNOWLEDGE

• radioactivity • application of scientific principles in the development of technologies

SKILLS AND ATTITUDES

• acquire and apply scientific and technological knowledge to the benefit ofself, society, and the environment

ICT OUTCOMES

• demonstrate competence in using basic information technology tools

Electromagnetic Radiation• Electromagnetic radiation is

essentially another term for light. In

addition to visible wavelengths of

light, however, it also includes

energy of shorter wavelengths such

as X-rays and gamma rays, and

longer wavelengths such as infrared

and radio waves.

• Electromagnetic radiation occurs

when an atom emits a photon.

• Electromagnetic radiation has the

properties of both waves and

particles.

• Photons have different energy levels

and wavelengths.

• Low-energy photons produce

familiar, harmless radiation such as

radio waves and visible light. High-

energy photons are more harmful

and include X-rays and ultraviolet

light.

• It is important to note that the term

radiation can refer to

electromagnetic radiation, but it can

also refer to the emission of

subatomic particles such as protons

and neutrons.

Electricity and Magnetism• Electricity and magnetism are similar

in that they both involve the

interactions of particles with force

fields, or regions of space in which

objects feel a force. Electric fields

can affect electrically charged

objects, and magnetic fields can

affect magnetically susceptible

objects. Electricity and magnetism

are also related in another way. A

moving electric charge can produce

a magnetic field, and a moving

magnet can produce an electric field.

Electric generators and electric

motors make use of this relationship.

In an electric generator, mechanical

energy is used to turn a magnet,

which produces an electric field and

so generates electricity in a wire. In

an electric motor, electric current

flows near a magnet and causes the

magnet to move. The motion of the

magnet powers the motor.

SCIENCE BACKGROUND

Time

30–45 min

Key Ideas

The atoms of some elementsare radioactive, which meansthey undergo radioactivedecay.

Vocabulary

• radioactivity

Program Resources

WS 10.1-1 Study GuideWS 10.2-2 Radioactivity and

its HistoryNelson Science Probe 10

Websitewww.science.nelson.com

Related Resources

McClafferty, Carla Killough.

Something Out of

Nothing: Marie Curie and

Radium. Farrar, Straus,

and Giroux Books for

Young Readers, 2006.

B.C. Probe 10

Computerized

Assessment Bank


Create and Present:




Resource Center


Website


Animations

– Cathode rays


TEACHING NOTES

Getting Started

• Teacher Demo: Visualising Radiation– Give students or pairs of students a sheet of photosensitive paper.

Photosensitive paper is available from science education suppliers. Besure to keep the paper away from direct light.

– In a dimly lit room, have the students place two to five objects ofvarying sizes and shapes on the sheet of paper.

– When the students have finished placing their objects on the paper, openwindows to let sunlight into the room or allow students to carefully taketheir papers outside for five minutes.

– After a few minutes, the paper should begin to react to the sunlight.Follow the directions on the packaging to set the image.

– After students have finished their images, ask them to speculate as tohow the image-making process might have worked. Encourage studentsto follow lines of reasoning that led them to the basic concepts ofradioactivity, such as light from the Sun carrying energy that affects thephotosensitive paper.

• Possible Misconceptions– Identify: (a) Students might think that all radiation is harmful.

(b) Some students may think that all forms of radiation are made bypeople.

– Clarify: (a) Most kinds of radiation, such as radio waves, visible light,and infrared light, are not harmful to humans. Higher energy radiation,including microwaves, ultraviolet rays, X-rays, and gamma rays, can beharmful to humans. However, these forms of radiation are generallyharmful only if humans are exposed to large amounts of them at once,or to low levels of them for a long time. In fact, small targeted doses ofhigh-energy radiation can destroy or shrink tumors and other harmfulgrowths. Radiation in small doses is also used in radiographs (X-rays)and CAT scans that doctors rely on when diagnosing diseases. (b) Many natural materials produce radiation. The Sun is a source ofradiation. Uranium, radium, plutonium, and polonium, which are usedin some technologies, are examples of naturally occurring radioactiveelements. Some kinds of rock, such as granite, produce small amounts ofradiation because of the elements in them.

– Ask What They Think Now: (a) Ask, If someone in your family stated thatall radiation is harmful, how would you respond to that statement? Studentsshould be able to explain that many forms of radiation are not harmful,even in large doses. Students should also be able to explain clearly thatalthough radiation can be harmful, when it is carefully controlled it is anessential medical tool. (b) Ask students to think about natural sources of radiation exposure intheir lives. Ask, How does your lifestyle and where you live affect yourexposure to naturally occurring radiation?

Guide the Learning

• This section provides background for students to understand the eventsleading to the discovery of radioactivity. Students may not realize thatradioactivity is a relatively recent discovery compared to discoveries in

2

1


Social StudiesConnectionsThough radiation in small

doses is not harmful, in

large amounts, it can be

devastating. Have students

research the 1986 accident

at the Chernobyl nuclear

power station. Have them

write a summary of the

effects of radioactive

emissions on that city to

this day.



CHECK YOUR UNDERSTANDING—SUGGESTED ANSWERS

1. The wavelength decreases.

2. X-rays have shorter wavelengths, higher frequencies, and greater energy than visible light waves.

3. Scientists once thought that gases were poor conductors of electricity, but during the mid-to-late 1800s,

scientists learned that gas in a partial vacuum would conduct electricity well.

4. Atomic nuclei can produce several kinds of electromagnetic radiation, including X-rays and gamma rays.

5. An electron beam will bend away from a negatively charged plate and toward a positively charged plate.

Therefore, the plate toward which the beam in the diagram is bending must be the positively charged plate.

6. Scientists put a small paddle-wheel in a cathode ray. The ray caused the wheel to spin, indicating that cathode

rays are made of particles.

7. Students can infer that since cathode-ray tubes produce X-rays, Crookes tubes probably do also. X-rays can be

harmful in large doses, so students should stand several meters away to reduce their exposure.

8. (a) The electron’s speed will decrease extremely rapidly.

(b) The energy in the X-ray comes from the electron, which loses energy when it slows down. The electron’s

kinetic energy has been converted into the energy of radiation.

9. Visible light has a longer wavelength, a lower frequency, and less energy than an X-ray has. Both are forms of

energy called electromagnetic radiation: both travel as waves at the speed of light (through a vacuum)

10. X-rays will expose photographic film. They can travel through soft materials, such as paper and skin, but not

hard materials, such as jewellery and bone. To create an X-ray image, X-rays are fired at something, such as a

human hand, that is in front of a plate containing photographic film. When the film is developed, the X-rays will

have exposed all the areas where they can penetrate and will have left unexposed all the areas they cannot

penetrate.

11. radium and polonium

12. Radioactivity: when an atom releases radiation from its nucleus

13. Temperature, pressure, and chemical changes do not affect the amount of radiation emitted by a radiation

source.

other areas of science. This section also lays the groundwork for anunderstanding of the many contemporary uses of radiation.

• As students examine Figure 2, remind them that electricity and magnetismare related. In the figure, the beam in the cathode-ray tube bends becauseof a pair of electrically charged deflection plates. A magnet would producea similar effect.

Consolidate and Extend

• Discuss the everyday applications of radiation. Encourage students tothink of careers that involve working with radiation (such as a radiologistor a radiology technician).

• Have students engage in debate. Some students should argue for thebeneficial uses of radiation therapy, and others should argue against the useof technology that may cause some people to be exposed to large amountsof radiation. Consider having students record the key points in the debateand then repeat the debate later in the unit after working through section11.1. Have students compare the points made in the two debates.

• Have students complete the Check Your Understanding questions.

3



ESL

• Students may look automatically for cognates to relate difficult science terms to similar words they alreadyunderstand. Cognates are words that are related because they were derived from the same source. Forinstance, they may try to make the connection between radio and radioactivity. If you notice studentsforming a connection that is not helpful to their understanding of the concepts, explain that these wordsare only very loosely related and then guide them to a more appropriate connection in the text, such as raysand radiate for radioactive.

Extra Support

• Students may envision parts of the electromagnetic spectrum as distinctly different things, and they mayhave difficulty understanding that the division between various types of electromagnetic radiation (andbetween various colors of visible light) is not clear-cut. Have students study Figure 6. Then ask then whatthey think the wavelengths between ultraviolet light and X-rays might be. Guide them to the concept thatthe electromagnetic spectrum is a continuum with no distinct dividing lines.


What To Look For in Student Work

Evidence that students can• identify the parts of a cathode-ray tube• explain why a beam of electrons in a cathode-ray tube may be deflected in one direction or another• explain several contemporary uses for radiation and radioactivity• describe safety procedures taken by professionals who work with radioactive substances• describe the electromagnetic spectrum• define radioactivity

ASSESSMENT FOR LEARNING

Making Study Cards

• Ask students to pay close attention to the sequence of events described on pages 275 and 276 in theStudent Book. Tell them to think about the event that allowed another event to take place as they read.Students who have trouble memorizing a sequence of events might benefit from kinesthetic learningmethods. Have students make study cards for the material in this section so that they can manipulate theevents in the sequence. Each card should have the name of a scientist on one side of a card and theappropriate discovery on the other. After students make their study cards, encourage them to lay the cardsout in the appropriate sequence. Then have students use their study card timelines to talk with a partnerabout how each discovery built on another. The cards can also be used as flash cards to prepare for an exam.

Strategies for Success



Radioactivity and the Nucleus Page 28010.2


• explain radioactivity using modern atomic theory• represent and interpret information in graphic form

KNOWLEDGE

• radioactivity


• use the periodic table and ion charts• use models to demonstrate how systems operate

Isotope Symbols• Throughout the chapter, atomic

number (A) is given along with the

chemical symbol and mass number

(Z). Because all atoms of the same

element have the same number of

protons, atomic number can be

identified from the chemical symbol

using the periodic table. Including

atomic number is a convenience that

allows students to see more clearly

the relationship between isotopes of

an element and to solve nuclear

equations more easily. Typically,

however, atomic number is not

displayed.

Detecting Neutrons• The main way humans detect matter

is through use of visible light, electric

fields, and magnetic fields.

Neutrons, like all subatomic particles

are too small to see. Because they

are neutral, they are unaffected by

electric fields or magnetic fields.

These challenges made detection of

the nucleus difficult.

SCIENCE BACKGROUND

Time

30–45 min

Key Ideas

Atoms of a single elementthat differ in mass are calledisotopes.

Vocabulary

• nucleus• proton• neutron• isotope

Program Resources

WS 10.2-1 Study GuideWS 10.2-2 Radioactivity and

the Nucleus Nelson Science Probe 10


Related Resources

“Islands of Stability.”

NOVA scienceNOW.

NOVA, 2006. Video

B.C. Probe 10

Computerized

Assessment Bank


Create and Present:




Resource Center


Website


Animations

– The Rutherford

experiment

TEACHING NOTES

Getting Started

• Teacher Demo: Rutherford Experiment Analogy• Draw a dot about the size of a coin on the board. Stand at the opposite

end of the room. Ask students to consider the following thoughtexperiment: If you were to fire a grain of salt toward the board from whereyou were standing, how likely is it that the salt grain would hit the spot onthe board? Allow students to respond.

• Then ask them to consider what would happen if the spot were the size ofthe board or if the board were filled with many of the smaller dots. Ask,Would you be more likely or less likely to hit a spot with the grain of salt?Allow students to discuss briefly.

• Explain the analogy for students as it relates to what Rutherford observed.Tell students that the grain of salt represents a positively charged particle inRutherford’s experiment and that the small spot on the board representsthe nucleus of an atom. Note that the items chosen to represent parts ofthe atom are not meant to suggest an actual size or distance scale.

1



• Possible Misconceptions– Identify: When students hear the word nucleus, they might think of the

nucleus of a cell, equating the two structures. – Clarify: The word nucleus is used to describe two very different structures.

The nucleus of a cell contains the cell’s genetic material (DNA). Thenucleus of an atom is made up of the atom’s protons and neutrons. Anatom is orders of magnitude smaller than a cell. In fact, a single cell can bemade up of trillions of atoms. Explain that the word nucleus comes from aLatin word meaning “kernel” and refers to the central or important part ofsomething.

– Ask What They Think Now: Ask, How is the nucleus of a cell different fromthe nucleus of an atom? How are they similar?

Guide the Learning

• Section 10.2 presents nuclear reaction equations using N to represent thechemical symbol, Z to represent the mass number, and A to represent theatomic number. To prepare students for this notation, introduce it herewhile referencing Figure 4. Write the following on the board: Z

AN. Havestudents identify which part of Figure 4 corresponds to each part of thenotation.

• Students might be tempted to think that, because the atomic numberrepresents the number of protons, the mass number must represent thenumber of neutrons. Reiterate that the mass number is the sum of thenumber of protons and the number of neutrons, and that the number ofneutrons can be found by subtracting the atomic number from the massnumber:

number of neutrons � Z � A

• Sample Problem—Practice problem solution The symbol for beryllium-9 is 9

4Be. From the periodic table, we know thatberyllium has 4 protons. Remember that the top number in the symbol isthe mass number, which is the sum of the number of protons and thenumber of neutrons. Since 9 � 4 � 5, we know that there are 5 neutrons.


• Review with students the terminology discussed in the section (proton,neutron, and isotope). Ask them to describe the relationship between eachterm and nucleus, atomic number, and mass number.

• Students might begin to confuse terminology presented in this sectionwith previously learned terms such as ion. Remind students that ions areatoms with positive or negative charges. Ions of an element have the samenumber of protons and may have the same number of neutrons. Point outthat every atom is an isotope of some element. Thus, every ion is also anisotope. The opposite statement, however, is not necessarily true. Anisotope (atom) is not necessarily an ion.


3

2

Language ArtsConnectionWord roots, particularly

those from Greek and

Latin, are very important to

scientific terminology. Have

students look up the

meanings of the following

roots: pro-, deut-, tri-, and

iso-. Ask them how

knowing the meanings of

these roots can help them

remember terms from this

section.




1. In Thompson’s raisin bun model, the raisins represent negatively charged particles (electrons), and the bun

represents positively charged matter.

2. Thompson’s assumption was reasonable because equal amounts of positive and negative charge would make

the atom neutral overall. This in turn supported the idea that matter as a whole is basically neutral.

3. The diagram shows that many positively charged particles were able to pass through the thin sheet of gold

with little or no deflection. A large nucleus would increase the chance that incoming particles would come

near the nucleus or strike it. Very few particles were deflected, however, indicating that few actually came

near or struck the nucleus. This suggested that the nucleus was very small. Because like charges repel one

another, the deflection backward of positively charged particles indicated that the nucleus has an overall

positive charge.

4. In the planetary model of the atom, the Sun represents the nucleus, and the planets represent electrons.

According to this model, the force holding the atom together is the electric force between the positively

charged nucleus and the negatively charged electrons.

5. A proton is a single particle with a positive charge. A hydrogen atom contains both a proton (its nucleus) and

an electron.

6. 1.83 � 103 electrons

7. The neutron was difficult to detect because it is neutral.

8. Unlike a proton or an electron, a neutron has no electric charge.

9. The atomic number indicates the number of protons in the nucleus. The mass number of an atom is the sum

of the number of protons and the number of neutrons.

10. Answers may vary. Sample answer: Isotopes are atoms of the same element that have different numbers of

neutrons.

11. Diagram should have a nucleus made up of 8 protons and 10 neutrons and should have 8 electrons around the

nucleus.

12. The nucleus of an atom of chlorine-35 has 18 neutrons. The nucleus of an atom of chlorine-37 has 20

neutrons.

13. Table 2 Isotopes of Elements

14. All isotopes of the same element have the same number of protons. For a neutral atom, the number of

protons equals the number of electrons. Because the electrons determine an atom’s chemical properties, the

chemical properties of an atom of a given element are the same regardless of the number of neutrons.

Isotope name Symbol Number of protons Number of neutrons

astatine-21121185As 85 126

uranium-235235

92U 92 143

magnesium-252512Mg 12 13

radon-20920986Rn 86 123

chlorine-373717Cl 17 20

deuterium21H 1 1

silicon-303014Si 14 16

palladium-10210246Pd 46 56

iodine-12712753I 53 74

tantalum-180180

73Ta 73 107

tungsten-18218274W 74 108



Analyze Tables

• Students can practice analyzing isotope symbols. Have students work with partners to analyze the materialin the table. Encourage students to cover the Comment column in the text and write their own commentsdescribing what they can tell about each isotope from its symbol. Then have students share with theirpartner what they wrote and correct together any misconceptions they had. Students should be able toexplain how the isotopes in the table are the same and how they are different.

Reading and Thinking Strategies


Evidence that students can • describe what Rutherford’s gold foil experiment revealed about the structure of an atom • identify the differences between protons, neutrons, and electrons • describe the difference between atomic number and mass number• explain what isotopes are and write symbols for isotopes


ESL

• Have students complete a 3-column table with column headers Particle, Charge, and Where found (i.e.,nucleus or outside nucleus) for quick reference.

Extra Support

• Provide support for students as they analyze the chemical symbol, mass number, and atomic number for anatom. Re-create the symbol on page 281 on the board as 6 � 6 � 12

6C. Use one colour of pen or chalk to circlethe bottom “6.” Ask students what the number represents. Draw a line connecting this circled “6” to thefirst “6” in the equation, and circle that number in the same colour. Then ask students what the other “6”in the equation represents. Circle that “6” in a different colour. Then put a box around the “12” in a thirdcolour. Label it “mass number.” Present students with several other examples and have them work throughinterpreting each symbol in this same manner.



Radioactive Decay Page 284

NEL


• explain radioactivity using modern atomic theory

KNOWLEDGE

• radioactivity• conservation of mass


• write and balance nuclear equations• use the periodic table and ion charts• use appropriate types of graphic models and/or formulas to represent a given

type of data, including the Bohr model

ICT OUTCOMES

• demonstrate competence in using basic information technology tools

10.3

Chapter 10 Radioactivity and the Atom 11

Time

90–120 min

Key Ideas

There are three basic typesof radioactive decay andthese processes can bewritten as nuclear reactionequations.

Vocabulary

• radioactive decay• parent nucleus• daughter nucleus• alpha particle• beta particle• gamma ray

Program Resources

WS 10.3-1 Study GuideWS 10.3-2 Radioactive DecayBLM 10.3-1 Alpha, Beta, and

Gamma DecayBLM 10.3-2 Writing Nuclear

EquationsNelson Science Probe 10


Related Resources

Wilson, Jerry D., and

Anthony Buffa. College

Physics, 5th Ed. NJ:

Prentice-Hall, Inc., 2002.

B.C. Probe 10

Computerized

Assessment Bank


Create and Present:




Resource Center


Website


Animations

– A Geiger Counter

– Half-life and

Radiochemial Dating

TEACHING NOTES

Getting Started

• Teacher Demo: Modeling Penetrating Abilities– Guide students to consider the effect of particle (or wavelength) size on

ability to penetrate different materials. If you have the followingmaterials available, use them to demonstrate. Otherwise, show images orask students to visualize the materials: Group A—a piece of windowscreen, plastic wrap, and a piece of construction paper; Group B—popcorn kernels, sand or salt, and light. The mesh on the window screenshould be large enough to allow sand and salt crystals to pass through.

– Ask students to predict which materials in Group B will be able topenetrate each material in Group A.

1

Types of Radioactivity• The alpha, beta, and gamma decay

discussed in the Student Book are

not the only types of radioactive

decay. Positron decay and electron

capture are two additional types of

radioactive decay.

• Positron decay is actually another

mode of beta decay. The beta decay

discussed in the Student Book (��

decay) involves emission of a

negatively charged electron that is

created in the nucleus. In positron

decay (�� decay), the nucleus emits

a positron, or a positively charged

electron ( 0�1e). In general, isotopes

that undergo �� decay have too

many neutrons relative to number of

protons to be stable. Isotopes that

undergo �� decay typically have too

many protons relative to the number

of neutrons to be stable.

• In electron capture (EC), the nucleus

absorbs an orbital electron. Electron

capture is sometimes referred to as

K-capture. K refers to the innermost

electron shell from which a nucleus

would typically capture an electron.

An electron from a distant orbit,

however, can also be captured by

the nucleus.

SCIENCE BACKGROUND


Connections: PersonalPlanningSpending your career

studying radioactive

isotopes might not seem

glamorous at first, but

physicists who specialize in

nuclear medicine might

disagree. These scientists

save lives with their

knowledge of radioactivity

and radioactive decay.


– With student volunteers assisting as necessary, alternately try to pour (orfocus) each material in Group B through each material in Group A. Askstudents what they can conclude about particle (or wavelength) size andability to penetrate materials. Remind students of this exercise as theyconsider the penetrating ability of different kinds of radiation.

• Possible Misconceptions– Identify: Students might mistake nuclear decay equations for chemical

equations. – Clarify: Nuclear reactions generally involve an atom’s nucleus (i.e., its

protons and neutrons). Chemical reactions involve only an atom’selectrons. Therefore, nuclear equations generally show the atomicnumbers and mass numbers of the atoms involved. Chemical equationsgenerally do not show atomic numbers or mass numbers.

– Ask What They Think Now: Ask, How is a nuclear reaction different from achemical reaction?

Guide the Learning

• Introduce and explain each type of radioactive decay. Use the generalequation and the sample problem to illustrate the reaction. You can useBLM 10.3-1 Alpha, Beta, and Gamma Decay as an overhead to refer to asyou describe each type of decay.

• Have students perform Investigation 10A: Penetrating Ability of NuclearRadiation. (See teaching notes for Investigation 10A on page 15.)

• Sample Problem 1—Practice problem solutionWe can find the symbol and atomic number for radium on the PeriodicTable (Ra; 88). When an atom undergoes alpha decay, the products are adaughter nucleus and an alpha particle, 4

2He. The total charge and totalnumbers of protons and neutrons must be equal on both sides of theequation.226

88Ra ��22286Rn � 4

2He

Radium has been transmuted into radon.

• Sample Problem 2—Practice problem solutionWe can find the symbol and atomic number for xenon on the periodictable (Xe; 54). When an atom undergoes beta decay, the products are adaughter nucleus and a beta particle. 13354Xe ��

13355Cs � 0

�1e

Xenon has been transmuted to cesium.

• Sample Problem 3—Practice problem solutionWe can find the symbol and atomic number for cobalt on the periodictable (Co; 27). When an atom undergoes gamma decay, the product is anatom in the ground state and a gamma ray. 6027Co ��

6028Ni* � 0

�1e6028Ni* ��

6028Ni � 0

0�

Cobalt has been transmuted to Nickel.

2




1. When a radioactive atom undergoes radioactive decay, its nucleus emits radiation (alpha particles, beta

particles, and/or gamma rays).

2. It would take 7 000 beta particles to equal the mass of one alpha particle.

3. Gamma rays are not particles because they do not have mass. They are waves of electromagnetic radiation.

When a nucleus emits gamma rays, its mass does not change; it only loses energy.

4. Sample response: In transmutation, an atom changes from one element to another.

5. During alpha decay, the atomic number (Z ) decreases by 2 and mass number (A) decreases by 4.

6. A helium atom has electrons, but an alpha particle does not. A helium atom is stable, but an alpha particle is

not.

7. (a) 18072W ��

17670Hf � 4

2He

(b) 14762Sm ��

14360Nd � 4

2He

(c) 2011Na ��

169F � 4

2He

8. Sample response: In beta decay, the nucleus emits an electron (a beta particle).

9. The electron came from the decay of a neutron into a proton, an electron, and a neutrino. Because the

nucleus gains a proton, it becomes a different element.

10. (a) 6428Ni ��

6429Cu � 0

�1e

(b) 31H ��

32He � 0

�1e

(c) 5926Fe ��

5927Co � 0

�1e

11. Atomic number and mass number do not change as a result of gamma decay. An atom emits gamma

radiation to return to a ground state from an excited (high energy) state.

12. 6026Fe ��

6027Co � 0

�1e

6027Co* ��

6027Co � 00�

13. (a) beta (b) alpha (c) alpha and beta (d) gamma

(e) alpha (f) gamma (g) alpha (h) alpha, beta, and gamma

14. (a) 23994Pu (b) 228

88Ra (c) 0�1e

(d) 00� (e) 4

2He (f) 21383Bi

(g) 0�1e (h) 239

93Np (i) 9943Tc*

15. In a cloud chamber, a radioactive source emits charged particles that cause the gas in the chamber to

become ionized. The ions cause vapor to condense and leave visible tracks. In a bubble chamber, a charged

particle passes through a superheated liquid, leaving tracks that show the direction of deflection of the

particle. A Geiger counter registers bursts of electric current created by radiation.

16. Gamma rays are not charged particles, so they cannot produce ions inside a gas chamber (which leads to the

formation of tracks).

17. Alpha particles leave larger tracks than beta particles because they produce a great deal of ionization over a

shorter distance.

18. Both Geiger counters and cloud chambers detect radiation by utilizing the ability of some forms of radiation

to ionize atoms.

19. Some Geiger counters cannot detect alpha radiation because alpha particles cannot penetrate the window at

the end of the cylinder.


• For students who need extra practice working methodically throughnuclear equations, you can use as a handout BLM 10.3-2 Writing NuclearEquations.


3




Evidence that students can• define alpha particle, beta particle, and gamma ray• determine whether a nuclear equation represents alpha, beta, or gamma decay • write nuclear equations for alpha, beta, and gamma decay• identify materials that can stop the penetration of alpha particles, beta particles, and gamma rays • explain why mass number and atomic number do not change during gamma decay


Adjusting Reading Pace

• Remind students that adjusting their reading rate for sections of difficult text can help with understanding.Have students work with partners to identify areas of text they found difficult. Then have students rereadthese sections more slowly. Students should then summarize and explain these sections to their partners.


Extra Support

• Encourage students to make flash cards for the three main types of radioactive decay (e.g., a card with“alpha particle” on one side and “a helium nucleus, 4

2He” on the other side) and for characteristics such as“does not change mass number or atomic number (gamma decay)” and “emits a negatively charged particle(beta decay).” Students can work in pairs to find relevant characteristics from the text to use for their flashcards.

Extra Challenge

• Introduce these students to an additional decay process: positron emission. A positron is a positively charged particle represented by the symbol 0

�1�. Challenge students to write theequations for the positron emission of polonium-207:20784Po ��

20783Bi � 0

�1�

Have students explain how the result of positron emission differs from that of beta decay. (The atomicnumber decreases by one following positron emission and increases by one in beta decay.)


Strategies for Success

Summarizing

• Have students write brief summaries for each type of radioactive decay. Use BLM 10.3-1 Alpha, Beta, andGamma Decay as an overhead that students can referece as they write their summaries.


NEL

10A

Chapter 10 Radioactivity and the Atom 15

Investigation: Penetrating Ability of Nuclear Radiation Page 298


• explain radioactivity using modern atomic theory• perform experiments using the scientific method• demonstrate safe procedures• demonstrate competence in the use of technologies specific to investigative

procedures and research• demonstrate scientific literacy

KNOWLEDGE

• radioactivity• elements of a valid experiment


• recognize dangers• use the Internet as a research tool

Time

30–45 min

Key Ideas

The atoms of some elementsare radioactive, which meansthat they undergo radioactivedecay.

There are three basic typesof radioactive decay andthese processes can bewritten as nuclear equations.

Skills and Processes

ConductingRecordingAnalyzingEvaluatingSynthesizingCommunicating

Lesson Materials

For teacher demo• set of radioactive samples

(alpha, beta, and gammasources)

• Geiger counter• 10 sheets of paper• 10 sheets of aluminum foil• 10 lead sheets

Program Resources

BLM 10.3-1 Alpha, Beta, andGamma Decay

Investigation BLM 10APenetrating Ability of Nuclear

RadiationRubric 18: Conduct an

InvestigationRubric 19: Conduct an

Investigation—Self-Assessment

SSP Rubrics 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, & 20

Nelson Science Probe 10Websitewww.science.nelson.com

Ionization• An ion is an atom with a positive or

negative charge. Ions with opposite

charges attract each other.

• When a charged particle, such as an

alpha or beta particle, enters the gas-

filled tube of the Geiger counter, the

particle ionizes gas atoms. In

ionization, a particle removes an

electron from an atom, creating

an ion.

• In a Geiger counter, ions are

attracted to particles or areas of

opposite charge. The ions that form

in the gas-filled tube are attracted to

charged plates, creating an electric

current that produces the pulse or

“count.”

Detecting Radiation• The activities of some industries

expose workers to high levels of

radiation. Workers in these industries

typically wear dosimeters, devices

that monitor radiation exposure. The

simplest dosimeters are film badges.

Upon exposure to radiation, the film

darkens. The degree of darkening

indicates the level of exposure.

• A rad is a unit used to express the

amount of radiation absorbed by a

certain quantity of material. A rem is

the unit used to express the effects

of radiation on living things.

Electromagnetic Spectrum• Unlike alpha and beta radiation,

gamma rays are not particles.

Gamma rays are electromagnetic

radiation, which is a form of energy.

Electromagnetic radiation travels in

waves and can be described in

terms of wavelength, or the distance

between two consecutive wave

peaks. The electromagnetic

spectrum includes all the

wavelengths of electromagnetic

radiation.

• The visible part of the spectrum

includes those wavelengths of

electromagnetic radiation (“light”)

that humans can detect.

• Gamma rays are high energy rays

with very short wavelengths. X-rays

have longer wavelengths than

gamma rays, but both types of rays

are beyond the visible part of the

spectrum.

• Visit the Nelson Science Probe 10

website for links to more information

about the electromagnetic spectrum.

SCIENCE BACKGROUND



INVESTIGATION NOTES

Student Safety

• The radioactive sources used are very weak. However, care needs to betaken around any radioactive sources. Do not come any closer to themthan needed, and keep them in storage until needed.

• Do not allow students to handle the radioactive sources. Do not allowthe radioactive source to come into contact with bare skin.

• Review the section on Radiation Hazards in the BC Science SafetyResource Manual. A link to this document is available at:www.science.nelson.com.

• Remind students not to allow watches anywhere near the Geiger counter.Some watches (typically older watches) contain radioactive materials thatallow the watch faces to glow in the dark. The Geiger counter will detect theradiation given off by such watches, producing a false reading.

Question

• Ask students how much of each type of material they think will be needed tostop alpha, beta, and gamma radiation.

Experimental Design

• During the investigation, be sure to hold the Geiger counter at the samedistance from the radioactive source for every reading. Point out to studentsthat you are doing this, and ask them why this is important. (During aninvestigation, one should keep all conditions except one—here, type ofmaterial—constant.)

Materials

• Some Geiger counters come equipped with a holder that has a place for theradioactive source. If the Geiger counter you have available does not,maintain consistency during the investigation by using two ring stands withclamps to hold the radiation sources and the Geiger counter.

Procedure

• For Step 2, guide students to conclude that the acceptable “blocked”radiation should be equal to the level of background radiation theydetermined in Step 1. Ask students why they are unable to blockbackground radiation in this instance. (The Geiger counter is detectingradiation from all sides of the “blocking” material.)

Analysis

(a) The decay rate seemed to decrease. The radiation travels outward from thesource in all directions. The farther from the source the Geiger counter is,the less radiation will strike its detector.

(b) Although everyone was exposed to some radiation, the teacher was probablyexposed to more because he or she was handling the radioactive sources.

(c) alpha particles, beta particles, gamma rays

Related Resources

B.C. Probe 10

Computerized

Assessment Bank


Create and Present:




Resource Center


Website


History ConnectionsThe harmful effects of

radiation have not always

been known. Once they

were recognized, however,

it became important to

learn how to prevent

radiation from affecting

people working with

radioactive materials. Have

students research the

history of radiation safety

protocols and procedures.



ESL

• Be sure students understand the meaning of penetrate before they begin the investigation. Tell students thatpenetrate means “move into” or “move through.” For beginning ESL students, reinforce the meaning bypouring water through a thin piece of cloth while nodding your head and saying The water penetrates. Pourpopcorn kernels or other small objects onto the cloth while shaking your head and saying The popcorn doesnot penetrate.

Extra Support

• Remind students of the demonstration carried out at the beginning of Section 10.3. Before students begintheir analyses of the investigation, have them work with partners to create analogies by matching thematerials and types of radiation used in this investigation to the materials (screen, plastic wrap, paper,popcorn kernels, sand, light) used in the demonstration.


Evaluation

(d) Sample answer: The Geiger counter “counted” even when no sources werenearby. We took this to be background radiation and used the averagenumber of clicks as a control. We subtracted this average number of clicksfrom the counts we recorded for each source. We considered a type ofradiation to be blocked when no more counts were registered than for thecontrol (no source nearby).

(e) Sample answer: The tube should be placed in the holder instead of theteacher’s hand so that the teacher’s hand does not interfere with the reading.

Synthesis

(f) Background radiation could account for counts when none of the sourceswas nearby.

(g) X-rays are more penetrating than alpha and beta particles but lesspenetrating than gamma rays.

(h) Sample answer: If I worked in a hospital that used radioactive sources, I would try to protect myself with lead-lined protective clothing, becauseenough lead will stop alpha, beta, and gamma radiation.


Evidence that students can• describe the relative penetrating abilities of alpha, beta, and gamma radiation • explain the importance of controls in investigations



Half-Life Page 290


• explain radioactivity using modern atomic theory• demonstrate scientific literacy• represent and interpret information in graphic form

KNOWLEDGE

• radioactivity


• use the periodic table and ion charts • use line graphs to extract and convey information• deduce relationships between variables given a graph or by constructing

graphs

ICT OUTCOMES

• demonstrate the ability to formulate questions and to use a variety of sourcesand tools to access, capture, and store information

10.4

Time

90–120 min

Key Ideas

The rate of decay of aradioactive sample ispredictable and is describedby the half-life of theradioactive isotope.

Vocabulary

• half-life• decay series

Program Resources

BLM 10.4-1 RadioactiveDecay and Half-Life

WS 10.4-1 Study GuideWS 10.4-2 Half-LifeWS 10.4-3 Half-Life

CalculationsWS 10.4-4 TechConnect:

BrachytherapyNelson Science Probe 10


Calculating Half-Life and DecayEquations• The number of parent nuclei in a

sample decays exponentially over

time. At any time t, one can

calculate the number of parent nuclei

remaining in a sample (P ) using the

equation P � Poe–t, where is a

constant that is unique to the

particular parent isotope and Po is

the number of parent nuclei initially

present in the sample. The decay

constant is equal to the natural

logarithm of two (ln 2) divided by the

half-life of the isotope.

• Because each parent nucleus decays

to form a daughter nucleus, the

number of parent nuclei is inversely

proportional to the number of

daughter nuclei in a sample, once

the number of initial daughter nuclei

in the sample is accounted for. One

can calculate the number of

daughter nuclei present (D) at time t

using the equation D � Do � P

(et � 1), where Do is the number of

daughter nuclei initially present in

the sample. If there were no

daughter nuclei initially present and if

no parent or daughter nuclei are lost

during decay, then D � P � Po at

any time t.

SCIENCE BACKGROUND


TEACHING NOTES

Getting Started

• Teacher Demo: Modeling Half-Life– Have all of the students in the class stand in a line. The students should

all be facing the same direction. (If there is an odd number of studentsin your class, stand in line with the students so that there is an evennumber of people in line.) Explain that, every minute, one-half of thepeople in line will sit down. Ask students to predict how many minutesit will take for three-quarters of the people in line to be sitting down.(You may wish to convert the fraction into an actual number. For

1

Related Resources

B.C. Probe 10

Computerized

Assessment Bank


Create and Present:




Resource Center


Website




example, if your class contains 24 students, you would ask how manyminutes it will take for 18 of the students to be sitting down.)

– Once students have made their predictions, carry out the demonstration.Have the class time one minute, and then choose half the students atrandom to sit down. After another minute, choose half of the remainingstudents at random to sit down. At this point, one-quarter of theoriginal number of students should be standing. If your class is largeenough, continue for one more minute.

– Have the remaining students return to their seats, and explain to theentire class that they just modeled the behaviour of a radioactivesubstance with a half-life of 1 minute. Ask students to volunteer whatthey know about the term half-life. Explain that the half-life of aradioactive substance is the time required for one half of the radioactiveatoms present to decay

• Possible Misconceptions– Identify: Carbon dating can be used to study all things that were alive in

the past. Students may apply knowledge of carbon dating to situations inwhich it would be impossible to carbon date, such as when studyingancient life such as dinosaurs.

– Clarify: Carbon-14 has a relatively short half-life. Although students mayhave heard of carbon dating, they may not understand that carbon-14can only be used to accurately date organic materials that are youngerthan 60 000 years.

– Ask What They Think Now: Ask students if it would be appropriate tocarbon date the remains of an organism that lived 150 000 years ago.They should recognize that carbon dating would not be an effectivedating method for that particular organism.

Guide the Learning

• You can use BLM 10.4-1 Radioactive Decay and Half-Life as an overhead toillustrate half-life.

• Sample Problem 1––Practice problem solution(a) First, determine how any half-lives have passed. The fraction left is

� �

We can see that 2 half-lives have passed. Now, calculate the totalamount of time that has passed: 2 � 1.8 h � 3.6 hFrom the graph, we can see that at about 3.6 hours, the mass isreduced to 12.5 mg.

(b) Since the half-life of fluorine-18 is 1.8 h, we can determine the

number of half-lives: � 3 half-lives

Now calculate the mss remaining.

m � � � (50 mg) � � � (50 mg) � 6.25 mg

The mass remaining is 6.25 mg. We can also see on the graph that theapproximate mass remaining after 2 half-lives is about 6 mg.

• Sample Problem 2—Practice problem solution(a) First, determine the number of half-lives represented by 320 years.

1 8

1

23

5.4 h1.8 h

1

221

412.5 mg50 mg

2

Math Connections

Radioactive decay follows

an exponential curve

(a curve with the equation

y � ex). Have students

make graphs of

exponential functions and

compare them to the

decay curves shown in

this section. Have

students research other

reactions and processes

that follow exponential

curves.



One half-life is 160 years, so 320 years is 2 half-lives. Then, calculatethe activity level of the sample after two half-lives.

a � � � (80 MBq) � � � (80 MBq) � 20 MBq

The activity of the sample after 320 years will be 20 MBq. (b) First, determine how many half-lives have passed since the activity of

the sample was 640 MBq.

� 8 � 23

So, three half-lives have passed since the activity was 640 MBq. Three half-lives is equal to 3 � 160 years � 480 years. The activity level of thesample was 640 MBq 480 years ago.

• Sample Problem 3—Practice problem solution

From the graph, we can see that 25 % of the original carbon-14 remainedafter about 11 000 to 12 000 years.

The decrease from 100 % to 25 % is a ratio of � �

Therefore, the time it takes is 5730 � 2 half-lives � 11 460 years.

The bone fragment is about 11 000 years old.

• Use WS 10.4-3: Half-Life Calculations to check student learning.

• Have students perform Investigation 10B: The Half-Life of Popcorn toapply what they have learned about rate of decay. (See teaching notes forInvestigation 10B on page 22.)


• Students have now had a chance to study radioactive decay and how thisphenomenon can be used by scientists to learn more about Earth’s past.Have students reflect on how scientific discoveries lead to newtechnologies, and that these new technologies in turn lead to more newscientific discoveries.


3

yearshalf–life

1

221

425 %

100 %

640

80

1

4

1

22


1. Activity (the number of decays per second) is measured in becquerels. One Bq equals one decay per second.

2. (a) 86 Bq (b) 1.7 � 10�2 Bq (c) 1.0 � 102 Bq (d) 1.1 � 10�1 Bq (e) 75 Bq

3. (a) about 160 000 atoms (b) about 400 000 atoms (c) about 10 minutes (d) about 30 000 atoms

4. 1.9 g

5. (a) 448 Bq (b) 14 Bq (c) about 106 days (2 half-lives)

(d) 1792 Bq (e) 159 days

6. Carbon-14 has a relatively short half-life. After a few half-lives (a few tens of thousand of years), only tiny

amounts of C-14 would remain. In addition, carbon-14 dating is used to date materials from sources that

were once living. Granite was never alive, so carbon-14 cannot be used to date a granite rock.

7. about 4 000 years

8. about 11 000 years (11 460 years)

9. about 3 % (3.125 %)



ESL

• To visually indicate the meaning of half-lives, give ESL students a series of tiles or squares of paper, andhave them illustrate half-life by moving half, then half again, then half again, (each in a specific period oftime). Then, have students repeat the activity, labeling the stable isotope tiles as they work through eachhalf-life.

Extra Support

• Remind students as they work through the problems that the type of radioactive compound in eachproblem does not change the underlying mathematical formulas they should apply. Each compound has itsown half-life, but half-life itself is always a standard percentage or fraction of the total.

TechCONNECT: BrachytherapyPAGE 297

• Radiation treatments themselves are not painful, although the side effects of radiation therapy can bedifficult to manage for some patients. After treatment, patients may worry that they themselves areradioactive. After brachytherapy, some radiation may temporarily be passed through urine or saliva, but theamounts passed are small and generally not harmful to healthy adults.

• Brachytherapy kills cancer cells by destroying the cells’ genetic material, DNA. The energy given off byradioactive isotopes damages the DNA of cancer cells, making them unable to grow and divide. In fact,radiation therapy affects all types of body cells, not just cancer cells. However, most normal body cells areable to withstand the effects and repair themselves. Cancer cells are affected much more profoundly.Brachytherapy is a particularly effective cancer therapy because it targets cancer cells while minimizing theamount of genetic damage done to healthy body cells.

• Scientists and medical researchers are looking for other ways to use brachytherapy. There is some promisingevidence that brachytherapy may be helpful in treating abnormal narrowing of the arteries after angioplasty.

• Have students complete WS 10.4-4 TechConnect: Brachytherapy.


Reading Graphs

• Have students examine Figure 5 and describe the trend shown in the graph. Ask them to predict what thecurve might look like if it extended to 6 minutes. Students should be able to predict that the line willcontinue to curve downward, but it will become less steep as time passes.



Evidence that students can• define the term half-life• use given information related to a sample’s half-life and amount of parent and daughter isotopes to determine the age of a sample• use given information related to the age of a sample to determine the ratio of parent to daughter isotopes




Investigation: The Half-Life of Popcorn Page 300


• explain radioactivity using modern atomic theory • perform experiments using the scientific method • represent and interpret information in graphic form

KNOWLEDGE

• radioactivity• elements of a valid experiment


• communicate results• use bar graphs, line graphs, pie charts, tables, and diagrams to extract and

convey information• deduce relationships between variables given a graph or by constructing

graphs

10B

Time

45–60 min

Key Ideas

The rate of decay of aradioactive sample ispredictable and is describedby the half-life of theradioactive isotope.


PredictingConductingRecordingAnalyzingEvaluatingSynthesizingCommunicating

Lesson Materials

per group• 100 popcorn kernels• container such as an empty

film canister or a Petri dish

Program Resources

BLM 10.4-1 RadioactiveDecay and Half-Life

Investigation BLM 10B TheHalf-Life of Popcorn

Rubric 18: Conduct anInvestigation

Rubric 19: Conduct anInvestigation–Self-Assessment

SSP Rubrics 5, 6, 9, 10, 11, 12,13, 14, 15, 16, 17, 18, 19,& 20

Nelson Science Probe 10Websitewww.science.nelson.com

Radioactive Decay• The decay of a specific radioactive

nucleus cannot be predicted.

However, when large numbers of

nuclei are present, the overall decay

of the sample can be predicted

statistically.

• The half-life of an isotope is the time

required for one half of the parent

nuclei present to decay to daughter

nuclei. Note that half-life cannot be

used for single nuclei. It applies only

to large numbers of nuclei.

• Although the half-life of a particular

isotope is a constant, the rate of

decay of a sample is not. This is

because the rate of decay is an

absolute number, but the half-life is a

relative number. The rate of decay is

defined as the number of decays per

minute or per second. It is a function

of how many parent nuclei are left.

When there are many nuclei left,

there will be many decays per

second. When few nuclei are left,

the decay rate will be lower. The

half-life is constant, however,

because the time required for the

number of nuclei to decrease by half

is fixed.

SCIENCE BACKGROUND

Related Resources

B.C. Probe 10

Computerized

Assessment Bank


Create and Present:




Resource Center


Website


INVESTIGATION NOTES

Student Safety

• Clean-up following the activity should involve sweeping the floor.Kernels could be a slipping hazard.

• Make sure students do not eat unpopped kernels. They could be achoking hazard. To discourage students from eating the raw popcorn,remind them that the kernels have been handled by other students andhave probably been on the floor.



Question

• Note that the rate of radioactive decay is a function of the number of parentnuclei present. However, unlike the “decay” modeled in this activity,radioactive decay follows a constant half-life curve.

Prediction

• Sample answer: The rate of decay will decrease when there are fewer parentnuclei left.

Materials

• If popcorn is unavailable, you may substitute coins, M&Ms, dice, or anyother objects with distinctive sides. If this substitution is made, you shouldtell students what state corresponds to decay (e.g., for M&Ms, the side withthe M could be undecayed and the side without the M could be decayed).

• You may wish to count out the popcorn kernels for each group ahead oftime and then store kernels in small containers such as 35 mm film canistersfor future use.

Procedure

• Some kernels will land such that their “points” face straight up in the air.You may instruct students to count these kernels as decayed or undecayed asyou see fit.

• Make sure students separate the parent and daughter kernels after eachshake.

Analysis

(a) Over time, the number of parent kernels decreased.

(b) The rate at which daughter kernels were produced decreased with time.

(c) Sample answer: It took 11 shakes for all the parent kernels to decay. This isabout the same as the rest of the groups.

(d) Sample answer: Based on the graph, it took about 1.8 shakes to reduce thenumber of parent kernels to about 50. It took about 3.6 shakes to reducethe number of parent kernels to about 25.

(e) Sample answer: The half-life of the popcorn is about 1.8 shakes.

Time (shakes)

Number of Parent Kernels vs. Time

Nu

mb

er o

f Pa

ren

t K

ern

els

Rem

ain

ing 100

9080706050403020100

0 21 3 4 5 6 7 8 9 10 11

♦

•

•

♦

♦♦

♦

♦ ♦ ♦ ♦ ♦

Social StudiesConnectionsNuclear power plants

produce radioactive waste

with a fairly long half-life.

The long half-life

complicates decisions

about where to store the

waste. Have students

research some of the

proposed storage

solutions for radioactive

waste and discuss the

pros and cons of each

solution.


Evaluation

(f) The popcorn was similar to parent nuclei because its “decay rate” dependedon the number of parent kernels remaining. It is different because popcornkernels are not radioactive, they are much larger than radioactive nuclei,and the definition of decay in the investigation is arbitrary.

Synthesis

(g) Sample answer: No, my results are not exactly the same as my classmates’.This is probably because the orientation of the popcorn kernels is random.

(h) Sample answer: If this experiment had been performed with 10 000 kernelsof popcorn, the results from different students would probably have beenmore similar.

(i) Sample answer: Because the criteria for “decaying” would be narrower, fewerkernels would qualify each round. If kernels take longer to decay, the half-life will be longer.

(j) Sample answer: If we used a computer to generate random numbers, wecould assign a certain range of numbers to represent decayed nuclei, andrecord how many decayed nuclei were produced at each iteration. Eachiteration would also have to contain a smaller number of random numbersthan the previous iteration. The number of undecayed numbers in theprevious iteration would determine the number of numbers generated inthe next iteration.



Evidence that students can• explain half-life in terms of rates of radioactive decay • use half-life graphs to determine the half-lives of substances and to determine how many parent nuclei and daughter nuclei were

present in a sample after a given amount of time• define concepts operationally in the design and analysis of their radioactive decay models• create graphs with appropriate scale and axes


ESL

• Allow beginning ESL students to respond to Conclusion questions by drawing simple pictures toaccompany or to replace text.

Extra Support

• To support the students in writing their conclusions, encourage them to use graphic organizers to organizethe information before composing responses. For example, have students create a Venn diagram for theEvaluation question.

• Use BLM 10.4-1 Radioactive Decay and Half-Life as an overhead for students to refer to complete theiranalyses.




Chapter 10 Review Chart

• Have students complete WS 10.0-1 Matching Challenge: Radioactivity toreview the chapter vocabulary.

• For extra support, have students use the vocabulary list for the chapter tocomplete BLM 10.0-1 Radioactivity Concept Map showing how all thevocabulary terms are related.

• Have students review their Study Guides to recall what they have learned inthis chapter.

• Have students complete the Chapter 10 Quiz to review the vocabulary andconcepts in this chapter.

• Encourage students to visit the online quiz centre on the Nelson Sciencewebsite and complete the Chapter 10 Self-Quiz.

• Have students use BLM 10.0-X Chapter Key Ideas to review the key ideas inthe chapter.

Review Key Ideas and Vocabulary—Suggested Answers

1. Diagram should contain a nucleus with 6 protons and 8 neutrons. Thereshould be 6 electrons outside the nucleus. Added together, the number ofprotons and the number of neutrons equals the mass number. The numberof electrons and the number of protons are equal.

10CHAPTER

Review Page 302

Time

45–60 min


The Chapter Review providesan opportunity for students todemonstrate theirunderstanding of and theirability to apply the key ideas,vocabulary, and skills andprocesses.

Program Resources

BLM 10.0-1 RadioactivityConcept Map

WS 10.0-1 MatchingChallenge: Radioactivity

WS 10.0-X Chapter Key IdeasChapter 10 QuizNelson Science Probe 10


2. Isotopes are atoms of the same element that have different masses due to different numbers of neutronsin their nuclei.

3. A

4. During alpha decay, the nucleus emits a helium nucleus, decreasing its atomic number by 2 and itsatomic mass by 4. During beta decay, the nucleus emits a beta particle (an electron), adding a proton tothe nucleus and thereby increasing its atomic number by 1.

5. C

6. D

Use What You’ve Learned—Suggested Answers

7. One molecule of heavy water is two atomic mass units heavier than one molecule of normal water. (Thiscould also be described as a ratio:

� 1.11. Therefore, heavy water is 1.11 times greater in mass than normal water.)

8.

16 � 2 � 2

16 � 1 � 1

23290Th ��

22888Ra �

42He 1.4 � 1010 year

22888Ra ��

22889Ac �

0�1e 5.8 year

22889Ac ��

22890Th �

0�1e 6.1 h

22890Th ��

22488Ra �

42He 1.9 year

22488Ra ��

22086Rn �

42He 3.6 d



9. C

10. (a) 6 (b) 9.4 g (c) 1600 Bq

11. B

12. (a) 4720Ca ��

4721Sc � 0

�1e (b) about 7.5 days

(c) about 4.5 days (d) 13.5 days

(e) 110 decays per second

13. C

14. C

Think Critically—Suggested Answers

15. Radiation is emitted from an atom’s nucleus. Chemical changes involve electrons. Involving a radioactiveatom in a chemical reaction will not change the amount of radiation emitted.

16. Possibilities for student research include: determining ages of rocks and fossils; determining ages oforganic materials, such as preserved human remains, cloth, and ancient “campfires”; using radioactiveelements as tracers in medical diagnoses; and using radiation in cancer therapies.

17. Sample answer: Carbon-14 dating could not be used for dinosaur bones because the half-life of carbon-14is far too short. To determine the age of dinosaur fossils, scientists can use radioactive dating to find theage of the rock surrounding a fossil.

Reflect on Your Learning—Suggested Answers

18. Sample answer: I know now that radiation does not just exist in science labs. There are many naturalsources of radiation. Radiation can be harmful, but there are some beneficial applications of radioactivity,such as cancer treatments, dating many materials, and detecting smoke in homes.

ESL

• Write the Key Ideas on the board or write them on sentence strips and post the strips on the wall. Write thevocabulary terms on sentence strips or cards. Have students post the vocabulary words under the applicableKey Idea. If students think a term belongs with more than one Key Idea, have them make additionalvocabulary cards and post them. Allow students to express whether or not they agree or disagree with theplacement of vocabulary terms. Once all vocabulary terms have been posted, have students explain howeach vocabulary term relates to the Key Idea. Allow beginning ESL students to express their ideas withdrawings or simple words and phrases.

Extra Support

• Have students work with partners to describe what concept each diagram or equation in the Key IdeasSummary represents. Encourage them to cover the given notes as they try to come up with their explanations.Have them identify the vocabulary words from the list on page 32 that apply to each diagram.


22088Rn ��

21684Po �

42He 54 s

21684Po ��

21282Pb �

42He 0.16 s

21282Pb ��

21283Bi �

0�1e 10.6 h

21283Bi ��

21284Po �

0�1e 60.5 min

21284Po ��

20882Pb �

42He 0.3 s


Chapter

10 Blackline Masters


Chapter 10 Blackline Master 10.3-1 29Copyright © 2009 by Nelson Education Ltd.

Blackline Master 10.3-1

Name: Date:

ALPHA DECAY

BETA DECAY

GAMMA DECAY

Alpha, Beta and Gamma Decay


Writing Nuclear Equations


Name: Date:

Complete or write the nuclear equations as indicated.

1. alpha decay of radon-217

What is the symbol for an alpha particle?

The atomic number of radon (Rn) is , so radon has protons.

The mass number of radon-217 is .

Radon-217 has neutrons.

During alpha decay, the number of protons by , and the

mass number by .

Write the complete equation for the alpha decay of radon-217:

2. 4217Cl �� ? � 0

�1e.

The atomic number of chlorine (Cl) is , so chlorine has protons.

The mass number of chlorine-42 is , so chlorine-42 has total protonsand neutrons.

Chlorine-42 has neutrons.

During beta decay, the number of protons increases/decreases (circle one).

During beta decay, the number of neutrons .

Write the complete equation for the beta decay of chlorine-42:

Copyright © 2009 by Nelson Education Ltd.30 Chapter 10 Blackline Master 10.3-2




Name: Date: Name: Date:

Writing Nuclear Equations (continued)3. beta decay of silver-106

The atomic number of silver (Ag) is , so silver has protons.

The mass number of silver-106 is .

Silver-106 has neutrons.

During beta decay, the number of protons by 1, and the number of

neutrons .

Write the complete equation for the beta decay of silver-106:

4. the gamma decay of titanium-44

The atomic number of titanium (Ti) is , so titanium has protons.

The mass number of titanium-44 is .

Titanium-44 has neutrons.

What is the symbol for a gamma ray?

During gamma decay, the number of protons , and the

number of neutrons .

Write the complete equation for the gamma decay of titanium-44:


Copyright © 2009 by Nelson Education Ltd.32 Chapter 10 Blackline Master 10.4-1

Consider a sample of matter containing radioactive material. The sample initially contains16 radioactive nuclei. The half-life of the parent isotope is 10 minutes.


Name: Date:

At the start, the sample has 16 parentnuclei and no daughter nuclei.

During the first 10 minutes, half theparent nuclei decay:

� 8 parent nuclei remaining

After 10 minutes, 50 % of the originalparent nuclei remain.

16

2

During the next 10 minutes, half theremaining parent nuclei decay:


After 20 minutes, 25 % of the originalparent nuclei remain.

During the next 10 minutes, half theparent nuclei decay:


After 30 minutes, 12.5 % of the originalparent nuclei remain.

4

2

8

2

Radioactive Decay and Half-Life




Name: Date:

radioactivity involveschanges inan atom’s

Atoms with the samenumber of protons butdifferent numbers of

which ismade up of

some of which haveunstable nuclei, causing

them to undergo

are called

duringwhich a

may emit radiation inthe form of a(n)

to producea

which can involveelements with different

which may decayfurther to form

another daughternucleus as part of a

Complete the concept map to show the relationships among the Chapter 10 vocabulary.Begin with the box that has already been filled in.

radioactivity radioactive decay beta particlenucleus parent nucleus gamma rayprotons daughter nucleus half-livesneutrons alpha particle decay seriesisotopes

Radioactivity Concept Map


BLM 10.3-2 Writing Nuclear Equations1. 4

2He; 86; 86; 217; 131; decreases; 2; decreases; 4; 21786Rn ��

21384Po � 4

2He2. 17; 17; 42; 42; 25; increases; stays the same;

4271Cl ��

4218Ar � 0

�1e

3. 47; 47; 106; 59; increases; stays the same; 106

47Ag ��106

48Cd � 0�1e

4. 22; 22; 44; 22; 00�; stays the same; stays the same;4422Ti* ��

4422Ti � 0

0�

Chapter 10: Radioactivity BLM and WS Answer Key

BLM 10.0-1 Radioactivity Concept Map

radioactivity nucleusinvolveschanges inan atom’s

Atoms with the samenumber of protons butdifferent numbers of

which ismade up of

protons neutrons

radioactive decaysome of which have

unstable nuclei, causingthem to undergo

isotopes

are called

parent nucleus

duringwhich a

may emit radiation inthe form of a(n)

alphaparticle

betaparticle

gammaray

to producea

half-lives

which can involveelements with different

decay series

which may decayfurther to form

another daughternucleus as part of a

daughternucleus

or



Chapter 10 Answer Key 35NEL

WS 10.4-3 Half-Life Calculations

1. (a) � 4 half-lives

(1296 Bq) � � � (1296) � � � 81 Bq

(b) � 5 half-lives

(25)(1296 Bq) � 41 472 Bq

(c) � 0.25 � �The activity

will be 324 Bq in two half-lives, or 76 d.2. (a) approximately 18 hr

(b) � 4 half-lives

(5 � 108) � � � (5 � 108) � � � 3 � 107 atoms

WS 10.4-4 Tech Connect: Brachytherapy1. (c); With other types of radiation therapy, radiation has

to penetrate healthy tissues to reach a tumour,damaging many healthy cells in the process.

2. (c); Radioactive isotopes used in the body need todecay quickly enough so that the body does notexperience long-term exposure to concentratedsources of radiation. Seconds or microsecondswould be too short for the radiation to have thedesired effect.

3. (d); If the half-life of the radioactive isotope is longenough, the sample can be reused for otherpatients.

WS 10.0-1 Matching Challenge: Radioactivity1. (e); 2. (g); 3. (i); 4. (c); 5. (l); 6. (f );7. (j); 8. (b); 9. (a);

10. (d); 11. (k); 12. (h)

Chapter 10 QuizPart A: Modified True/False

1. True2. False; possible responses: mass number, numbers of

neutrons, radioactive particles3. False; 4

Part B: Completion4. electrons5. 1226. excited

Part C: Matching7. (c); 8. (a); 9. (b)

Part D: Multiple Choice10. A; 11. D; 12. B; 13. D; 14. A; 15. D; 16. B; 17. B Part E: Short Answer18. (a) The nucleus consists of protons and neutrons, but

no electrons. (b) During beta decay a neutronbreaks down and turns into a proton, an electron,and a neutrino. The proton stays in the nucleus.The electron and neutrino are emitted.

19. 12150Sn ��

12151Sb � 0

�1e

1

16

1

24

72 Hr

18 Hr

1

22

1

4

324 Bq

1296 Bq

190 d

38 d/half-life

1

16

1

24

152 d

38 d/half-life


sample trb 5r - nelson

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