energy of ions in different orbitals

springee

1. The problem statement, all variables and given/known data
Calculate the wavelength of light needed to excite a Li2+ ion from the 4s to the 5d orbital. Report your answer with 3 significant figures.



2. Relevant equations
E=hc/lambda
lambda=hc/E



3. The attempt at a solution
I think that the above equations are supposed to be used to figure out the wavelength. However, I need to figure out the energy (E) first. I don't know how to do this.
Can this be calculated just thinking of the orbitals as excited states??