Hafnium Ionization Energy

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

Hf -> Hf¹⁺ = 642 kJ/mol = 153.59 Kcal/mol
Hf¹⁺ -> Hf²⁺ = 1440 kJ/mol = 344.50 Kcal/mol
Hf²⁺ -> Hf³⁺ = 2250 kJ/mol = 538.28 Kcal/mol
Hf³⁺ -> Hf⁴⁺ = 3216 kJ/mol = 769.38 Kcal/mol