Radioactivity

1. High-energy radiation in the form of photons; often emitted with other types of decay.
5. The original unstable nuclide before radioactive decay.
6. The resulting nuclide formed after radioactive decay
8. The process by which an unstable nuclide becomes more stable by emitting radiation.
12. The repulsive force between positively charged protons in the nucleus.
14. The central part of an atom that contains protons and neutrons.
16. The spontaneous emission of particles and energy from an unstable atomic nucleus.
17. A type of nuclide; atoms of the same element with different numbers of neutrons.
18. A neutrally charged particle found in the nucleus that helps stabilize it.
20. A specific type of atom identified by the number of protons and neutrons in its nucleus.

2. A type of radiation consisting of two protons and two neutrons; has low penetration.
3. The region on a graph where the neutron-to-proton ratio predicts stable nuclides.
4. A type of radiation produced when a neutron changes into a proton and emits an electron.
7. The scientist who discovered alpha and beta radiation and proposed the nuclear atom.
9. A positively charged particle found in the nucleus of an atom.
10. The scientist who first discovered radioactivity by experimenting with uranium.
11. The tendency of a nucleus to resist radioactive decay.
13. A negatively charged particle located outside the nucleus of an atom.
15. The powerful force that holds protons and neutrons together in the nucleus.
19. The family of scientists who discovered radium and polonium and measured radiation.