Ionization Energy of Lithium problem

[wee00x]

The energy needed to strip all three electrons from a Li(g) atom was found to be 1.96*10^4 kJ/mol. The first ionization energy of Li is 520 kJ/mol. Calculate the second ionization energy of Lithium atoms (the energy required for the process)

Li+(g) ---> Li+2 + e-

Equation: frequency = (3.29x10^15s-1)Z^2(1/n^2i - 1/n^2f)

Ei + hv = Ef

My question: These equations can give me the energy of each energy level but how do I find the energy of required for ionization??

 

[Borek]

Ionization means energy is higher than the one needed for the electron to jump from n=1 to n=∞.

 

[wee00x]

But then how would that be calculated?

 

[Borek]

For very large n 1/n² is for all practical purposes equal to zero.

 

[Redbelly98]

Equation: frequency = (3.29x10^15s-1)Z^2(1/n^2i - 1/n^2f)

That equation only works when there is one electron. If there are two or more, you pretty much have to measure (or be told) what the ionization energy is.

So, in what situation does the above equation apply to lithium?