1. Ch. 21
Nuclear
Chemistry

2. Cl The Nucleus Nucleons: Protons and neutrons.
Nuclide: an atom, identified by the number of protons and neutrons in its nucleus.
Nuclides can be written with the name or symbol, followed by a dash with the mass number: Chlorine-35 or Cl-35, or as follows:
21-2 Cl
Atomic mass = 35 17
Atomic number =

3. The Nucleus
Mass Defect: the difference between the mass of an atom and the sum of the masses of its protons, neutrons and electrons.
Nuclear Binding Energy: the energy released when a nucleus is formed from nucleons.
Nuclear Shell Model: nucleons exist in different energy levels, or shells, in the nucleus.
21-3

4. Radioactive Decay
Nuclear Reaction: a reaction that changes the nucleus of an atom.
Transmutation: a change in the identity of a nucleus as a result of a change in the number of its protons.
Nuclear Particles
Type Symbol Charge
Alpha particle 42He +2
Beta particle 0-1β -1
Positron 0+1β +1
Neutron 10n 0
Gamma Ray γ 0
21-4

5. Radioactive Decay
21-5

6. Radioactive Decay
Radioactive Decay: the spontaneous disintegration of a nucleus into a slightly lighter nucleus, accompanied by emission of particles, electromagnetic radiation or both.
Nuclear Radiation: particles or electromagnetic radiation emitted from the nucleus during radioactive decay.
Radioactive Nuclide: an unstable nucleus that undergoes radioactive decay.
21-6

7. Radioactive Decay
Alpha emission (α): two protons and two neutrons bound together, emitted during some types of radioactive decay.
21-7

8. Radioactive Decay
Beta emission (β): an electron emitted from the nucleus during some types of radioactive decay.
21-8

9. Radioactive Decay
Positron emission : a particle that has the same mass as an electron, but has a positive charge and is emitted during some types of radioactive decay.
21-9

10. Radioactive Decay
Gamma Rays (γ): high energy electromagnetic waves emitted from a nucleus as it changes from an excited state to a ground state.
Example: Balance the following reaction:
21284 Po → 42He + ________
21284 Po → 42He Pb
1) Balance the following reaction:
25399 Es + 42He → 10n + ________
25399 Es + 42He → 10n Md
21-10

11. Radioactive Decay
Half-Life : the time required for half the atoms of a radioactive nuclide to decay.
21-11

12. Radioactive Decay
Decay Series: a series of radioactive nuclide produced by successive radioactive decay until a stable nuclide is reached.
21-15

13. Radioactive Decay
Nuclear Fission: a very heavy nucleus splits into more stable nuclei of intermediate mass, starting a chain rxn.
21-13

14. Radioactive Decay
Nuclear Fusion: low mass nuclei combine to form a heavier, more stable nucleus.
21-14

15. Ch. 21
The
End!