| A | B |
|---|
| nucleus | the tiny central core of an atom |
| proton | particle with a positive charge in the nucleus of an atom |
| neutron | neutral particle in the nucleus of an atom |
| electron | negatively charged particle which moves in the area around the nucleus of an atom |
| atomic number | the number of protons in an elements atom |
| atomic mass | the average mass of one atom of an elemen |
| valence electron | electrons farthest away from the nucleus and involved in the formation of chemical bonds |
| electron dot diagrams | a diagram using symbols and dots to represent the valence electrons of elements |
| atomic mass unit (amu) | unit used to measure the mass of particles in atoms |
| periodic table | table of elements in which the properties repeat in each period or row |
| group | vertical column of the periodic table |
| family | another name for a vertical column or group |
| period | horizontal row across the periodic table |
| alkali metal | the most reactive elements which are group 1 metals |
| alkaline earth metal | highly reactive elements found in group 2 |
| nonmetal | elements to the right of the zigzag line in the periodic table |
| halogen family | group 17 elements which have 7 valence electrons |
| noble gas | group 18 elements which have 8 valence electrons and are stable unreactive gases |
| metalloid | have some of the characteristics of metals and of nonmetals |
