Which electronic level would allow the hydrogen atom to absorb a photon but not to emit a photon?

An isotone of $${}_{32}^{76}Ge$$ is

Many elements have non-integral atomic masses because:

The electron energy in hydrogen atom is given by E = (-21.7 $$\times$$ 10^-12)/n² ergs. Calculate the energy required to remove an electron completely from the n = 2 orbit. What is the longest wavelength (in cm) of light that can be used to cause this transition?