Well, the real subject title should be: determining the wavelength and color of radiation emitted when an atom of X undergoes a transition from lowest excited state to the ground state.
Alrighty... What do we know? The energy needed to ionize an atom of element X when it is in its ground stat is 500 KJ/mol.
The energy needed to ionize an atom of element X in its lowest excited state is only 120 KJ/mol.
How do we find the wavelength?
I considered using Rydberg's equation to determine the wavelength but the equation only works for hydrogen. :( I'm really lost. Please help!