If a more complicated atom has two energy levels for its electrons at (-15) eV and (-30.1) eV, what is the wavelength of the photon (in nm) that is emitted when an electron transitions between these two levels?

Answer 1

The energy difference between levels is 15.1 eV. Convert that to Ephoton, in Joules.

Ephoton = 2.42*10^-18 J

Set that equal to h*c/(wavelength) and solve for the wavelength.

h is Planck's constant.
c is the speed of light

The photon will be in the very far "vacuum" ultraviolet.