Niobium Ionization Energy

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

Nb -> Nb¹⁺ = 664 kJ/mol = 158.85 Kcal/mol
Nb¹⁺ -> Nb²⁺ = 1382 kJ/mol = 330.62 Kcal/mol
Nb²⁺ -> Nb³⁺ = 2416 kJ/mol = 577.99 Kcal/mol
Nb³⁺ -> Nb⁴⁺ = 3695 kJ/mol = 883.97 Kcal/mol
Nb⁴⁺ -> Nb⁵⁺ = 4877 kJ/mol = 1166.75 Kcal/mol
Nb⁵⁺ -> Nb⁶⁺ = 9899 kJ/mol = 2368.18 Kcal/mol
Nb⁶⁺ -> Nb⁷⁺ = 12100 kJ/mol = 2894.74 Kcal/mol