| A | B |
|---|
| proton | positively charged particle in an atom |
| neutron | uncharged particle in the nucleus of the atom |
| electron | negatively charged particle in an atom |
| atom | basic unit of matter |
| nucleus (of atom) | contains protons and neutrons |
| element | pure substance that consists of one type of atom |
| isotope | atoms with same number of protons, but different numbers of neutrons |
| compound | substance formed by chemical combination of two or more elements |
| ionic bond | formed when one or more electrons are transferred from on atom to another |
| ion | positively or negatively charged atom |
| covalent bond | bond formed when atoms share a pair of electrons |
| molecule | smallest unit of most compounds |
| van der Waals forces | weak forces of attraction between molecules |
| atomic number | number of protons in an atom |
| atomic mass | calculated by adding protons + neutrons |
| valence electrons | electrons in the outer energy shell; participate in chemical reactions |
