| A | B |
|---|
| periodicity | tendancy to recur at regular intervals |
| periodic law | statement that the physical and chemical properties of the elements repeat in a pattern when they are arranged in order of increasing atomic number |
| period | horizontal row in the periodic table |
| group | elements in a vertical column of the periodic table |
| noble gas | element from group 18 that has a full complement of valence electrons and as such is unreactiive |
| metal | element that has luster, conducts heat and electricity, nad usually bends without breaking |
| transition element | any of the elements in groups 3 through 12 of the periodic table, all of which are metals |
| lanthanide | one of the first series of inner transition elements with atomic numbers 58 to 71 |
| actinide | any of the second series of inner transition elements with atomic numbers from 90 to 103; all are radioactive |
| nonmetal | element that in general does not conduct electricity, is a poor conductor of heat, and is brittle when solid. Many are gases at room temperature. |
| metalloid | element with some physical and chemical properties of metals and other properties of nonmetals |
| semiconductor | element that does not conduct electricity as well as a metal, but that does conduct slightly better than a nonmetal |
