| A | B |
|---|
| atom | Smallest unit of matter |
| element | Substance made of only one kind of atom |
| compound | Substance made of two or more elements |
| molecule | Group of atoms held together by covalent bonds |
| ion | An atom that has lost or gained and electron |
| proton | Positively charged atomic particle |
| electron | negatively charged particle |
| neutron | Atomic particle with no charge |
| polar | molecule with an uneven distribution of charges |
| nonpolar | A molecule with an even distribution of charges |
| hydrogen bond | Weak chemical attraction between polar molecules |
| nucleus | Core of an atom |
