Nuclear Energy

3. A chemical reaction or other process in which the products themselves promote or spread the reaction, which under certain conditions may accelerate dramatically.
7. A helium nucleus emitted by some radioactive substances, originally regarded as a ray.
8. The number of protons in the nucleus of an atom, which determines the chemical properties of an element and its place in the periodic table.
10. A nuclear reaction in which a heavy nucleus splits spontaneously or on impact with another particle, with the release of energy.
13. The emission of ionizing radiation or particles caused by the spontaneous disintegration of atomic nuclei.

1. The time it takes for half of a radioactive substance to decay.
2. A chemical element with the same number of protons but with different numbers of neutrons and atomic masses.
4. A subatomic particle of about the same mass as a proton but without an electric charge.
5. The center part of an atom which holds the protons and neutrons.
6. An electromagnetic radiation of the shortest wavelength and highest energy.
9. The total number of protons and neutrons in a nucleus.
10. A nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy.
11. A fast-moving electron emitted by radioactive decay of substances.
12. A subatomic particle with a positive electrical charge.