Holmium Ionization Energy

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

Ho -> Ho¹⁺ = 580.7 kJ/mol = 138.92 Kcal/mol
Ho¹⁺ -> Ho²⁺ = 1139 kJ/mol = 272.49 Kcal/mol
Ho²⁺ -> Ho³⁺ = 2204 kJ/mol = 527.27 Kcal/mol
Ho³⁺ -> Ho⁴⁺ = 4100 kJ/mol = 980.86 Kcal/mol