1. Chapter 21 Nuclear Chemistry
12th edition

2. 21.1 Radioactivity Review from Ch. 2 Subatomic particles
Atoms are neutral: # protons = # electrons
Isotopes – atoms with same number of protons but different number of neutrons
Particle
Position
Charge
Mass (kg)
electron
outside nucleus −1
9.11 x 10-31
nucleon
proton
inside nucleus +1
1.67 x 10-27
neutron

3. Nuclear Chemistry deals with only the nucleus.
radioactivity – spontaneous emission of radiation
nuclide – nucleus with specified number of protons and neutrons
radionuclide – radioactive nuclide
radioisotopes – atoms containing radioactive nuclei
radioactive decay – spontaneous decomposition to form a different, more stable, nucleus with the production of one or more particles
decay series – multiple decay steps through which radioactive nuclides go to reach a stable state

4. Decay Series

5. Common Particles in Radioactive Decay and Nuclear Reactions
Decay products: (See Tables 21.2 and 21.3, p. 879)
alpha (α) particle
42He or 42α
Common for heavy radionuclide
beta (β) particle
0-1β or 0-1e
High-speed electrons; atomic number increases when a decay product
gamma (g) ray
00g
High-energy photons; often accompanies other decay like electron capture
positron
01β or 01e
Atomic number decreases when a decay product
Decay reactants:
electron capture
0-1e
Addition of electron(s) with production of g rays
neutron capture
10n
Neutron capture causes transmutations and fission-based chain reactions

6. Fission of 235U initiated by neutron capture

7. Chain Fission Reaction

8. Examples: 6831Ga + 0-1e → _____ 21287Fr → 20885At + ______
Nuclear Equations – sums of both mass and atomic numbers on both sides of equation are equal
Examples:
6831Ga + 0-1e → _____
21287Fr → 20885At + ______
263106Sg → ______ + 42He

9. 21.4 Rates of Radioactive Decay
Radioactive decay follows 1st order kinetics.
All half-lives are equal.
N – # of radioactive nuclei
k – decay constant
Individual half-lives vary tremendously:
214Po 2 x 10-4 s
144Nd 5 x 1015 year

10. Half-lives

11. Practice exercise, p. 890

12. Practice problem 21.33

13. Practice problem, 90Sr from 1st atomic explosion

14. Mastering problem 21.41