Erbium Ionization Energy

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

Er -> Er¹⁺ = 588.7 kJ/mol = 140.84 Kcal/mol
Er¹⁺ -> Er²⁺ = 1151 kJ/mol = 275.36 Kcal/mol
Er²⁺ -> Er³⁺ = 2194 kJ/mol = 524.88 Kcal/mol
Er³⁺ -> Er⁴⁺ = 4115 kJ/mol = 984.45 Kcal/mol