Across
- 2. a chemical reaction or other process in which the products themselves promote or spread the reaction, which under certain conditions may accelerate dramatically.
- 4. the positively charged central core of an atom, consisting of protons and neutrons and containing nearly all its mass.
- 6. the time taken for the radioactivity of a specified isotope to fall to half its original value.
- 9. a fast-moving electron emitted by radioactive decay of substances. (The emission of beta particles was originally regarded as a ray.).
- 10. a helium nucleus emitted by some radioactive substances, originally regarded as a ray.
- 12. a subatomic particle of about the same mass as a proton but without an electric charge, present in all atomic nuclei except those of ordinary hydrogen.
- 14. a stable subatomic particle occurring in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron, but of opposite sign.
Down
- 1. 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.
- 3. a nuclear reaction in which a heavy nucleus splits spontaneously or on impact with another particle, with the release of energy.
- 5. gamma rays.
- 7. a nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy.
- 8. the emission of ionizing radiation or particles caused by the spontaneous disintegration of atomic nuclei.
- 11. the total number of protons and neutrons in a nucleus.
- 13. Atoms with the same number of protons but different numbers of neutrons