| A | B |
|---|
| element | something that can't be broken down |
| atom | smallest part of an element |
| nucleus | center of an atom |
| proton | a particle with a positive charge |
| neutron | a particle with no charge |
| electron | a particle with a negative charge |
| atomic number | number of protons in the nucleus of an atom |
| atomic mass | total mass of particles in an atom |
| mass number | number of protons and neutrons in the nucleus of an atom |
| energy level | in an elctron cloud; where an electron is likely to be found |
