Question

Using ideas of electronic structure, what happens to the radii of the atoms in group 1 or 2, when the group is descended?

Answer 1

Atomic radii increase going down a group

Explanation:

The general trend for atomic radius is that it increases going down a group in the periodic table. Why is this?

Each new period you come across going down the group contains electrons that occupy atomic orbitals that have a probability density that extends farther from the nucleus.

For groups 1 and 2 elements, the most loosely-bound electron will occupy an `s`-orbital (`1s` for period 1, `2s` for period 2, `3s` for period 3, and so on). The successive orbitals are larger in size, meaning the probability of an electron being farther from the nucleus gets greater as you go down the group.