| A | B |
|---|
| Periodic Law | states that when the elements are arranged according to their atomic numbers, elemets with similar properties occur at sregular intervals |
| valence electrons | the number of electrons in an atom's outer energy level |
| group | a vertical column on the periodic table |
| period | a horizontal row on the periodic table |
| main-group elements | elements in groups 1,2, 13-18 |
| alkali metals | group 1 of the periodic table; react with water to make alkaline solutions |
| alkaline-earth metals | group 2 of the periodic table; higly reactive and found normally as compunds |
| halogens | group 17 of the periodic table; most reactive group of non-metals |
| noble gases | group 18 of the periodic table; very stable non-metals due to full set of valence electrons |
| transition metals | groups 3-12 on the periodic table; do not have identical electron configurations in each group |
| alloy | metal that is mixed with one or more other elements, usually other metals |
