| A | B |
|---|
| John Dalton | proposed a theory of the atom that we use today |
| Dalton's Atomic Theory | six part set of ideas to help us understand the atom |
| Democritus | had an early theory of atoms that was proved to be mostly correct |
| Aristotle | had an early theory of matter that was accepted over one by Democritus |
| atom | smallest particle of an element that retains the properties of that element |
| cathode ray | a stream of electrons; work with them led to the discovery of the electron |
| electrons | smallest part of the atom; negatively charged |
| neutron | neutral part of the atom; located in the nucleus and similar in size to a proton |
| proton | positive part of the atom; located in the nucleus and roughly the same size as a neutron |
| atomic mass | total number of protons and neutrons in a nucleus |
| mass number | number of protons plus the number of neutrons |
| atomic number | number of protons in an atom |
| isotope | atoms of an element can have different numbers of neutrons in the nucleus |
| alpha particle | high energy helium nucleus |
| alpha radiation | an alpha particle shot from an unstable nucleus |
| beta particle | a electron that is emitted from an unstable nucleus |
| beta radiation | an electron shot from the nucleus |
| gamma radiation | energy shot from a nucleus in order to stabilize it |
| nuclear equation | shorthand way to express a decay series |
| radiation | rays and particles emitted by radioactive material |
| radioactivity | radiation spontaneously emitted by unstable nuclei |
| radioactive decay | a process by which energy is emitted by unstable nuclei |
