One of the emission spectral lines for Be3 has a wavelength of 253.4 nm for an electronic transition that begins in the state with n 5.

One of the emission spectral lines for Be3 has a wavelength of 253.4 nm for an electronic transition that begins in the state with n 5. What is the principal quantum number of the lower-energy state corresponding to this emission? (Hint: The Bohr model can be applied to one-electron ions. Don’t forget the Z factor: Z nuclear charge atomic number.)