Ionization energy doubt

Question

What is negative and positive ionization enthalpy?

Answer 1

Ionization energy is defined as the energy required to remove an electron from an atom. Therefore, a positive ionization energy implies that you are looking at an oxidation:

 

M + hv --> (M+)  +  e-

 

a negative ionization energy implies you are looking at the reverse process, namely a reduction:

 

(M+) + e-  -->  M + hv

 

notice that the placement of the energy term hv. It is in the reactant side when a process is endothermic (you gain energy) and on the product side when it is exothermic (you lose energy).