18-1
1. Band of stability: the area on a graph of neutron number versus proton number in which all stable nuclei lie.
2. Mass defect: the mass lost by conversion to energy when a nucleus forms from separated nucleons.
3. Nuclear binding energy: the energy emitted when nucleons come together to form a nucleus; also the energy needed to break a nucleus into individual separated nucleons.
4. Nucleons: the protons and neutrons that make up the nucleus of an atom.
5. Nuclide: any combination of protons and neutrons in a nucleus.
6. Strong nuclear force: the force of attraction among the particles of a nucleus that overcomes electrostatic repulsion and holds the nucleus together.
18-2
1. Annihilation of matter: the event that occurs when a particle collides with its antiparticle and both are changed into electromagnetic energy.
2. Beta particle: a high-energy electron emitted from the nucleus when a neutron changes to a proton.
3. Chain reaction: a self-sustaining nuclear or chemical reaction in which the product from one step acts as a reactant for the next step.
4. Critical mass: the smallest mass of radioactive material needed to sustain a chain reaction.
5. Gamma ray: high-energy electromagnetic radiation produced by decaying nuclei.
6. Nuclear fission: a nuclear reaction in which a very heavy nucleus splits into two smaller nuclei of approximately equal mass.
7. Nuclear fusion: the combining of two small nuclei to form a larger, more stable nucleus with the release of energy.
8. Radioactivity: the process during which unstable nuclei undergo spontaneous nuclear decay and emit particles and electro magnetic waves.
9. Transmutation: the process of changing one nucleus into another by radioactive disintegration or bombardment with other particles.
18-3
1. Half-life: the time required for half of a sample of radioactive atoms to decay.