Trends in atomic radius in the Periodic Table

Trends in atomic radius in Periodic table:

We have to ignore the noble gas at the end of each period because neon and argon don't form bonds.
In horizontal period: Atomic radius decreases from left to right due to:

Gradual increasing in positively nuclear charge that increase the attraction force for valence electrons

In vertical group: Atomic radius increases from up to down due to:

The effect of extra energy levels being added is more than the effect of extra positively nuclear charge

Increasing of the repulsion forces between valence electrons and inner core electrons

Ionic radius:
Positive ions (Cations):
It is an atom lost one electron or more
They are smaller than the atoms they come from Because:

Sodium is 2, 8, 1
Na+ is 2, 8.
The atom has lost a whole layer of electrons, and the remaining 10 electrons are being pulled in by the full force of 11 protons.
Negative ions (Anions):
It is an atom gained one electron or more
They are bigger than the atoms they come from Because:

Chlorine is 2,8,7
Cl- is 2, 8, 8.
Although the electrons are still all in the 3 - level, the extra repulsion produced by the incoming electron causes the atom to expand. There are still only 17 protons, but they now have to hold 18 electrons.