Question

An electron in Li2+ falls from n = 2 to the ground state. Calculate the wavenumber, (νˉ), of the emitted photon

Answer 1

use the equation in the following link:
http://www.kentchemistry.com/links/AtomicStructure/rydbergeq.png
where your n(final) is your ground state and your n(initial) is n=2
R=10 973 731.6 m-1
Don't forget to divide your answer into 1 to get the wavelength in metres :)