A Li2+ ion had its electron in an excited state. When the electron relaxed to the ground state (n = 1) a photon of light was emitted with an energy of 1.884×10−17 J. What energy level was the electron in before it transitioned to the ground state?

Question

A Li2+ ion had its electron in an excited state.  When the electron relaxed to the ground state (n = 1) a photon of light was emitted with an energy of 1.884×10−17 J.  What energy level was the electron in before it transitioned to the ground state?

DrBob222 · Answer

(1/wavelength) = RZ^2(1/n^2 - 1/n^2)
(1/wavelength) = RZ^2*(1/1^2 - 1/x^2) and solve for x.
R = Rydberg constant = 1.0973732
The first n is n = 1 and the second n is n = 2; that's where the 1/1^2 and 1/x^2 come from.
Z is the atomic number of the element; in this case that is 3 so Z^2 = 9.
You will need to convert energy to wavelength with E = hc/wavelength. Post your work if you get stuck.