| A | B |
|---|
| Period | rows across that increase in atomic number |
| All Elements in the same period | have the same number of electron shells |
| Group | columns that go up and down |
| All elements in the same group | have the same number of valence electrons in its outer shell |
| Valence electrons | electrons farthest from the nucleus |
| protons | positively charged particles in the nucleus |
| neutrons | particles in the nucleus that has no charge |
| electrons | small energetic particles that surround the nucleus, they have a negative charge |
| atomic number | tells how many protons an atom has |
| shell | the orbits of electrons around a nucleus of an atom |
| atomic mass | number of protons plus nuetrons |
| family is another name for | group |
