Question

find energy required to remove first three electrons from al.ionisation energy of al=30ev?

Answer 1

The ionization energy of a three-, four-, and five electron system iswhereAs with the two-electron system, we have not applied a relativistic correction to  but we have made a crude approximation of reducing the relativistic correction in  by 5% to 0.45 and where  is , so that the expression becomesThe agreement with the literature values of ionization energies is 99% or better in all cases. It is evident from the above discussion that as the number of electrons in the system increases the equations get more complicated and it is difficult to determine the various corrections.