| A | B |
|---|
| periodic table | an arrangement of elements in columns, based on a set of properties that repeat from row to row |
| period | a row in a periodic table of elements |
| group | a column of elements in a periodic table |
| periodic law | the pattern of repeating properties displayed by elements in the periodic table |
| atomic mass unit (AMU) | one twelfth the mass of a carbon-12 atom |
| metals | elements that are good conductors of heat and electric current |
| transition metals | elements that form a bridge between elements on the left and right sides of the periodic table |
| nonmetals | elements that are poor conductors of heat and electric current |
| metalloids | elements with properties that fall between those of metals and nonmetals |
| valence electron | an electron that is in the highest occupied energy level of an atom |
| alkali metals | the elements in Group 1A of the periodic table, not including halogen |
| alkaline earth metals | the elements in Group 2A of the periodic table |
| halogens | the elements in Group 7A of the periodic table |
| noble gases | the elements in Group 8A of the periodic table |
