- The atomic numbers of elements within Groups 1 and 2 increase from top to bottom.

- The number of valence electrons (outer shell electrons) increases by one for each element moving down the group.

- The atomic radii also increase down the groups, as the additional electron shells increase the distance from the nucleus.

Groups 13 to 18 (Boron Family to Noble Gases)

- The atomic numbers of elements within Groups 13 to 18 increase from left to right across the period.

- The number of valence electrons increases by one for each element moving across the period.

- The atomic radii generally decrease across the period, as the additional protons in the nucleus pull the electrons closer.

Exceptions:

- The atomic radii of the noble gases (Group 18) are larger than the elements preceding them in their respective periods due to their complete valence electron shells, leading to weaker interatomic forces.

- There are slight irregularities in the atomic radii trends for some transition metals due to their complex electronic structures.