Promethium Ionization Energy

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

Pm -> Pm¹⁺ = 535.9 kJ/mol = 128.21 Kcal/mol
Pm¹⁺ -> Pm²⁺ = 1052 kJ/mol = 251.67 Kcal/mol
Pm²⁺ -> Pm³⁺ = 2150 kJ/mol = 514.35 Kcal/mol
Pm³⁺ -> Pm⁴⁺ = 3970 kJ/mol = 949.76 Kcal/mol