| A | B |
|---|
| electron | negatively charged particle in an atom |
| proton | positively charged particle found in the nucleus of an atom |
| neutron | uncharged particle in the nucleus of an atom |
| nucleus | the center of an atom |
| atomic number | the number of protons in the nucleus of an atom |
| atomic mass | the mass of an atom |
| symbol | one or two letter combination that represnts an element |
| period | a row on the periodic table |
| group | a column on the periodic table |
| alkali metals | extremely reactive metals in Group 1; have 1 valence electron |
| valence electrons | electrons in the outermost layer of the electron cloud; electrons that take place in chemical bonding |
| alkaline earth metals | reactive metals found in Group 2; have 2 valence electrons |
| transition metals | metals found in Groups 3-12 |
| halogens | reactive nonmetals found in Group 17; have 7 valence electrons |
| noble gas | unreactive nonmetal found in Group 18; has 8 valence electrons |
| Mendeleev | the creator of the periodic table |
| rare earth metals | metals located at the bottom of the periodic table |
