The Energy Change for an Electronic Transition in a One-Electron

Multiple Choice

The energy change for an electronic transition in a one-electron atom or ion (H,He⁺,Li²⁺,etc.) from n_initial to n_final is given by ,where Z is the atomic number. Which one of the following species will have the longest wavelength emission line for the transition between the n_initial = 2 and n_final = 1 levels?

A) H
B) He⁺
C) Li²⁺
D) Be³⁺
E) B⁴⁺