| Term | Definition |
| group 1 | alkali metals |
| group 7 | halogens |
| group 8 | noble gases |
| atomic radius | increases right to left, bottom to top |
| ionic radius | increases top to bottom, right to left |
| Electronegativity | increases left to right, bottom to top |
| Periodicity | the repeating pattern of phsical properties shown by the different periods |
| melting points of elements in group 1 | the melting points decrease down the group as the atoms become larger and the strength of metallic bond decreases |
| melting points of elements in group 7 | the van der waals attractive forces between diatomic molecules increase down the group so the melting points increase |