| A | B |
|---|
| atomic mass | the average mass of one atom of an element |
| periodic table | a chart of the elements showing the repeating pattern of their properties |
| nucleus | the central core of an atom containing protons and usually neutrons; it is in the CENTER of an atom |
| neutron | a small particle in the nucleus of the atom, with no electrical charge |
| proton | a small, positively charged particle in the nucleus of the atom |
| electron | a tiny, negatively charged particle that moves around the nucleus of an atom |
| atomic number | the number of protons and neutrons in the nucleus of an atom |
| atomic mass unit (amu) | a unit used to measure the mass of particles in atoms; a proton or neutron has a mass of 1 amu |
| chemical symbol | a one- or two-letter representation of an element |
| group | elements in the same vertical column of the periodic table; also called family |
| family | elements in the same vertical column of the periodic table; also called group |
| period | a horizonal row of elements in the periodic table |
| valence electron | one of the electrons FARTHEST away from the nucleus of the atom; these electrons are involved in a CHEMICAL BONDING |
