Question

explain the. factors which affect. ionization energy?

Answer 1

Basically there are five factors which can affect the Ionization energy like size of an atom,The effective nuclear charge,Shielding effect,Penetration effect and electronic configuration of an atom.All these factors related to the number of electrones in the valence shell and between the valence shell and nucleus.

Answer 2

Basically how strong the valence electrons are attracted/bound towards the core That is effective core charge and overall ionization state overall positive charge leads to even more attraction and further compaction of the electron shell of the atom/molecule. Shielding factors are another important one. So called slater rules may help with The latter one :)