Oxygen Ionization Energy

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

O -> O¹⁺ = 1313.9 kJ/mol = 314.33 Kcal/mol
O¹⁺ -> O²⁺ = 3388.2 kJ/mol = 810.57 Kcal/mol
O²⁺ -> O³⁺ = 5300.3 kJ/mol = 1268.01 Kcal/mol
O³⁺ -> O⁴⁺ = 7469.1 kJ/mol = 1786.87 Kcal/mol
O⁴⁺ -> O⁵⁺ = 10989.3 kJ/mol = 2629.02 Kcal/mol
O⁵⁺ -> O⁶⁺ = 13326.2 kJ/mol = 3188.09 Kcal/mol
O⁶⁺ -> O⁷⁺ = 71333.3 kJ/mol = 17065.38 Kcal/mol
O⁷⁺ -> O⁸⁺ = 84076.3 kJ/mol = 20113.95 Kcal/mol