| A | B |
|---|
| Greek model | atoms were alike but diff. shape,size |
| Dalton | atoms of element were same, but diff. from another element |
| Thompson | discovered electrons |
| Rutherford | atoms mostly space |
| Bohr | electrons in definite orbits |
| Wave theory | electrons have energy levels |
| nucleus | contains atom's mass |
| atomic number | number of protons |
| isotope | atom with diff. number of neutrons |
| neutron | no electrical charge |
| electron | negative electrical charge |
| proton | positive electrical charge |
| mass number | protons plus neutrons |
| atomic mass | average mass of element's atoms |
| quark | subatomic particle |
| strong force | holds protons in nucleus |
| weak force | responsible for radioactive decay |
| electromagnetic force | holds electrons in motion around nucleus |
| gravity | weakest of four forces |
| alchemists | early chemists |
