The ionization energy is _________ to the atomic size of atom.

The ionization energy of O₂ is smaller than the ionization energy of atomic O; the opposite is true for the ionization energies of N₂ and atomic N. Explain this behavior in terms of molecular orbital energy diagrams of O₂ and N₂.

Rank the following elements in order of increasing ionization energy and increasing atomic size: 

Rank the following elements in order of increasing ionization energy and increasing atomic size: P, O, S.