chapter 19 radioactivity. chapter 19:1 fun fact: if the nucleus of the hydrogen atom was a ping pong...

Chapter 19

Radioactivity

Chapter 19:1

Fun Fact: If the nucleus of the hydrogen atom was a ping pong ball, the electron in the 1s orbital would be 0.3 mile away and have a mass of 2.5 billion tons.

The energies involved in nuclear processes are typically millions of times larger than those associated with normal chemical reactions.

Chapter 19:1

Nucleons: particles of neutrons and protons.Atomic #: # of protons.Mass #: # of protons + neutrons.Atoms that have identical atomic # but different

mass numbers are called isotopes.Nuclide: applied to each unique atom

Chapter 19:1

Carbon12C 13C 14C

Many nuclei are radioactive: they spontaneously decompose.

14C 14N + 0e where e, represents an electron, which is called a beta particle.

6 6 6

6 7 -1

Both the atomic number and the mass number must be equal.

19.1: Types of Radioactive Decay

Alpha () particle: a helium nucleus 4He A very common mode of decay for heavy

radioactive nuclides.

Radium-222 to give Radon-218.222Ra 4He + 218Rn

230Th 4He+ 226Ra

88 2 86

90 2 88

2

19.1: Types of Radioactive Decay

Beta () particle: 0e The net effect of -particle production is to

change a neutron to a proton. Results in no change in mass number and an

increase in 1 in atomic number234Th 234Pa + 0e

131I 131Xe + 0e

-1

90 91 -1

53 54 -1

-1

19.1: Types of Radioactive Decay

Gamma ray(): high-energy photon of light. Zero charge and zero mass number.

238U 234Th + 4He+ 20

-1

92 90 2 0`

19.1: Types of Radioactive Decay

Positron: particle w/ same mass as the electron but the opposite charge. 0e

+1

19.1: Types of Radioactive Decay

Electron capture: a process by which one of the inner-orbital electrons is captured by the nucleus.

201Hg + 0e 201Au + 080 -1 79 0`

19.3: Detection of Radioactivity and Concept of Half-life.

Objectives: To learn about radiation detection instruments.

To understand half-life.

Figure 19.2: A representation of a Geiger-Müller counter (Geiger).

Ar(g) Ar+(g) + e-

Argon doesn’t conduct a current, “pulse”

19.3: Detection of Radioactivity and Concept of Half-life.

Scintillation counter: uses sodium iodide (gives off light) when struck by a high-energy particle. Detector senses the flashes of light and counts the decay events.

Half-life: time required for half of the original sample of nuclei to decay.

Uses of Radioactivity19.4: Dating by Radioactivity.

Objectives: To learn how objects can be dated by radioactivity

Carbon-14 dating: can be used to date wood and cloth artifacts. Reacts with oxygen to form carbon dioxide.

Half-life of 5730 years.

Uses of Radioactivity19.5: Medical Applications of Radioactivity.

Objectives: To discuss the use of radiotracers in medicine.

Radiotracers-radioactive nuclides that can be introduced into organisms in food or drugs.

Examples: Iodine-131: illnesses of the thyroid. Thallium-201 damage to the heart muscle after a

heart attack. Technetium-99 similar. Table 19-4 p. 619

Uses of Radioactivity19-6: Nuclear Energy

Fusion: combining 2 light nuclei to form a heavier nucleus.

Fission: splitting a heavy nucleus into 2 nuclei

Figure 19.4: Unstable nucleus.

Figure 19.5: Representation of a fission process.

Figure 19.6: Diagram of a nuclear power plant.

Figure 19.7: Schematic of the reactor core.

Figure 19.8: Radioactive particles and rays vary greatly in penetrating power.

1. The Energy of the radiation2. The penetrating ability of the radiation3. Ionizing ability of the radiation4. Chemical properties of the radiation.

Total amount of mRem 125/year

Human activities: 67 mrem