Ytterbium Ionization Energy

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

Yb -> Yb¹⁺ = 603.4 kJ/mol = 144.35 Kcal/mol
Yb¹⁺ -> Yb²⁺ = 1176 kJ/mol = 281.34 Kcal/mol
Yb²⁺ -> Yb³⁺ = 2415 kJ/mol = 577.75 Kcal/mol
Yb³⁺ -> Yb⁴⁺ = 4220 kJ/mol = 1009.57 Kcal/mol