Aperiod three element has 738, 1451, and 7733 kj/mol as its first three ionization energies. what is the symbol of this element?

Mg The period 3 elements are those in the 3rd row of the periodic chart and they are sodium, magnesium, aluminium, silicon, phosphorus, sulfur, chlorine, and argon. Looking at a chart of the first ionization energies for all of the elements, it is fairly obvious that of the 8 candidates, the only ones that are possible are magnesium, aluminium, and silicon. And looking at those 3 elements in detail reveals that magnesium has 737.7, 1450.7, and 7732.7 kJ/mol as its first three ionization energies, which is a perfect match.

I'm not sure but i will try to find out

Determine the  wavelength of light emitted when an electron  in an li2+ ion  makes a transition from an orbital with n  =  6 to an orbital with n  = 5.