Neptunium Ionization Energy

The Neptunium Ionization Energy is the energy required to remove from atom one mole of electrons with subsequent production of positively charged ion of Neptunium.
Np -> Np⁺ + e^-
This process can be repeated many times, but the energy cost is increased dramatically. The general equation for the Neptunium is:
Np^N+ -> Np^(N+1)+ + e^-

Np -> Np¹⁺ = 597 kJ/mol = 142.82 Kcal/mol