What is the correlation between atomic size and ionisation enthalpy?

Name two ions which are iso-electronic with Ar (Z = 18).

Arrange,  l, l^-, l⁺ in increasing order of size.

Arrange the following in increasing order of size: Cl^-, S^2-, Ca²⁺, Ar

Arrange the following in decreasing order of ionic size:

Mg²⁺,  O^2-,  Na⁺, F^-,  N^3-.