Why does the atomic radius decrease as electrons are added to a shell?

why does the atomic radius increase as you go from the top to the bottom of a chemical family?

ionization energy is the energy it takes to remove one valence electron from an atom.
its trends are generally opposite to those of the atomic radius.
explain why:

atomic radius decreases along the group.

atomic radius increases down the group.

ionization energy increases along the group and decreases down the group.

Explanation:

1. As we add an electron the effective nucleus charge increases because when electrons increase protons also increase so the net nuclear charge on the valence electron also increases therefore the size will tend to decrease.

2. As we move from top to bottom number of shell keeps adding on as a result the atom becomes bigger and bigger due to increase in number of shell.so the size increases.

3.as we move from top to bottom the size increases as a result total nuclear pull on the valence electron decreases so it becomes easy to remove an electron so ionization energy decreases down the group. As we move along the period the effective nuclear charge increases as mentioned above in 1 therefore it becomes difficult to remove an electron so ionization energy increases as we move along the group.