nuclear chemistry. subatomic particles protons- plus charge in the nucleus neutrons- neutral...

Nuclear chemistry

Subatomic Particles

• Protons- plus charge

In the nucleus• Neutrons- neutral

• Electrons - negative charge

Outside the nucleus

• http://www.teachersdomain.org/resources/phy03/sci/phys/energy/radsource/index.html

• http://www.teachersdomain.org/resources/tdc02/sci/life/evo/radiodating/index.html

• http://www.teachersdomain.org/resources/phy03/sci/phys/matter/date/index.html

• http://www.teachersdomain.org/resources/phy03/sci/phys/matter/threemile2/index.html

Stability of Nuclei

http://www.eas.asu.edu/~holbert/eee460/decay.html

• Ratio of neutrons to protons determines stability = “belt of stability”

• Ratio of nuclei with atomic numbers greater than 83 makes those nuclei unstable (radioactive, radioisotope)

• Unstable nucleus decays forming products that are more stable; emits radiation

Radiation

• Radiation comes from the nucleus of an atom.

• Unstable nucleus emits a particle or energy

alpha

gamma

beta

He42

Types of Radiation

• Alpha particle ()– helium nucleus paper2+

• Beta particle (-)– electron

e0-1

1-lead

• Positron (+)– positron

e01 1+

• Gamma ()– high-energy photon 0

concrete

Alpha Emission

He Th U 42

23490

23892

parentnuclide

daughternuclide

alphaparticle

Numbers must balance!!

Beta Emission

e Xe I 0-1

13154

13153

electronparentnuclide

daughternuclide

Numbers must balance!!

e Ar K 01

3818

3819

positron

Positron Emission

Numbers must balance!!

daughternuclide

parentnuclide

Balancing Nuclear Equations

1) Use Table N to determine decay mode

2) In the reactants and products…

Atomic and mass numbers must balance

3) A new element will be formed…

according to the new atomic number

DECAY MODE

Learning Check 1

What forms when carbon -14 decays?

Solution 1

What forms when carbon -14 decays?

14C 0 + 14 N

6 -1 7

Worksheet: Balancing nuclear equations

Half-Life of a Radioisotope

The time for the radiation level to fall (decay) to one-half its initial value

decay curve

8 mg 4 mg 2 mg 1 mg

initial

1 half-life 2 3

http://www.eas.asu.edu/~holbert/eee460/decay.html

Examples of Half-Life

Isotope Half life

C-15 2.4 sec

Ra-224 3.6 days

Ra-223 12 days

I-125 60 days

C-14 5700 years

U-235 710 000 000 years

HALF- LIFE

Learning Check 2

How many half lives will it take for 50 grams of 99 Tc to decay to 6.25 g?

½ life amount time

Solution 2

How many half lives will it take for 50 grams of 99 Tc to decay to 6.25 g? 3 half lives

½ life amount time0 50 01 25 2.13 x 105

2 12.5 2 (2.13 x 105)3 6.25 3 (2.13 x 105)

½ life amount time

Transmutation – One element becomes another.

Natural

Alpha

Beta

Gamma

Positron

Artificial

Fission

Fusion

Nuclear Fission

Fission

larger unstable nuclei break up into smaller more stable nuclei; release of neutrons causes a chain reaction and energy release

235U + 1n 139Ba + 94Kr + 3 1n +

92 0 56 36 0

Energy

Fission

Nuclear Power

• Fission Reactors Cooling Tower

Nuclear Power

• Fission Reactors

Nuclear Fusion

Fusion

small nuclei combine

2H + 3H 4He + 1n +

1 1 2 0

Occurs in the sun and other stars, hydrogen bomb

Energy

Nuclear Power

• Fusion Reactors (not yet sustainable)

Nuclear Power

• Fusion Reactors (not yet sustainable)

Tokamak Fusion Test Reactor

Princeton University

National Spherical Torus Experiment

Fission vs. Fusion

• 235U is limited• danger of

meltdown• toxic waste• thermal pollution

• fuel is abundant• no danger of

meltdown• no toxic waste• not yet sustainable

FISSION

FUSION

• Atomic Bomb– chemical explosion is used to form a critical

mass of 235U or 239Pu– fission develops into an uncontrolled chain

reaction

• Hydrogen Bomb– chemical explosion fission fusion– fusion increases the fission rate– more powerful than the atomic bomb

Nuclear Weapons

Learning Check 3

Indicate if each of the following are

(1) Fission (2) fusion

A. Nucleus splits

B. Large amounts of energy released

C. Small nuclei form larger nuclei

D. Hydrogen nuclei react

Energy

Solution 3

Indicate if each of the following are

(1) Fission (2) fusion

A. 1 Nucleus splits

B. 1 + 2 Large amounts of energy released

C. 2 Small nuclei form larger nuclei

D. 2 Hydrogen nuclei react

Nuclear Chemistry Uses

• Dating– dating previously living materials (Carbon-14) – dating rocks and other geological formations

(Uranium-238)

Nuclear Chemistry Uses

Medical Application

• Radiation Treatment– larger doses are used

to kill cancerous cells in targeted organs (Cobalt-60)

• Radioisotope Tracers (absorbed by specific organs and used to diagnose diseases)– Iodine-131 detection and treatment of thyroid conditions– Technetium-99 detects presence of tumors

Radiation treatment using-rays from cobalt-60.

Nuclear Chemistry Uses

• Food Irradiation radiation is used to kill bacteria (Co-60 and

Cs-137)

• Consumer Products– ionizing smoke detectors - 241Am

• Radioactive Tracers

(tracers follow the path of a material in a system) – Map the path of

carbon in metabolic processes

(Carbon-14)– study plant growth,

photosynthesis (Phosphorus-31)

Nuclear Chemistry Uses

Nuclear power plant.

Diagram for the tentative plan for

deep underground isolation of nuclear

waste.