| A | B |
|---|
| Atom | The smallest representative particle of an element |
| Isotopes | Atoms of the same type but having different numbers of neutrons and therefore different weights. |
| Proton | A sub-atomic particle having a mass of 1 and a charge of +1 |
| Neutron | A sub-atomic particle having a mass of 1 and a charge of 0 |
| Electron | A subatomic particle having a mass of 0 and a charge of -1 |
| Nucleus | The location of the protons, neutrons and mass of an atom. |
| J. J. Thomson | Discoverer of the electron and the proton. |
| Democritus | The first philosopher to consider that atom. |
| Rutherford | Proposed the idea that that atom has a nucleus. |
