Almost every electron is SHIELDED from the nucleus because the electrons closest to the nucleus are repelling the others.
This Negative Repelling increases the radius/volume of the atoms, as they push out on each other.

Effective Nuclear Charge (Z-eff):
The number of protons in the nucleus
S < p < d < f < g < h
With the same n-value

Every period is adding electrons to the SAME electron-shell, but protons are increasing, so it increases in energy,
BUT
When it’s a new period the electron-shell changes, which has less energy.

The Atomic Radius:
Defined as half of the distance between two of the atoms of the element.

Radius is partially decided by Z-eff:
This DECREASES the volume Left -> Right because protons are pulling electrons in TIGHTER.
This INCREASES the volume Top -> Bottom because more and more SHELLS are added.

Ionic Radius:
Cations are SMALLER
Anions are BIGGER
The higher the radius the lower the melting point.

Ionization Energy:
The minimum amount of energy is needed to remove an electron from an atom in the gas phase.
Increases when going UP and LEFT on the periodic table generally, although Group 5 is higher than Group 6 because Group 5 only has unpaired p-orbitals, which are harder to remove, than one that is already paired.

Largest Magnitude of Energy Found:
When you are trying to remove core electrons instead of valence electrons.
So you can see that where the BIGGEST chance in energy is the number of valence electrons that that atom has.
I1 > I2 > I3, etc.

First Ionization Energy:
The minimum energy needed to REMOVE the first electron from a neutral atom.

Electron Affinity:
How much energy is released after an electron is added to the atom.
Increases when going UP and LEFT on the periodic table generally, but there are MANY exceptions.

Negative Affinity:
This means that you need to ABSORP energy to add an atom.
It’s WEAK