| A | B |
|---|
| JJ Thomson | CRT -- Cathode ray experiment |
| Hypothesized that all mass of an atom is at center and the rest empty space | Ernest Rutherford |
| particle that has the same mass as a proton | neutron |
| area of probability where electrons may be found | electron cloud |
| atomic number | number of protons in an element |
| isotopes | atoms of same element with different number of neutrons |
| mass number | number of protons plus neutrons in an element |
| amount of time required for half a sample to decay | half-life |
