Energy levels of the hydrogen atom:
En = -me4/(2ħ2n2) = -13.6 eV/n2

Ground state wave function of the hydrogen atom:
ψ100(r,θ,φ) = (πa03)-1/2 exp(-r/a0).
a0 = ħ2/(me2) = 52.92 pm

Hydrogenic atoms:
En  = -Z2*13.6 eV/n2
a0 = 52.92/Z pm

The spectrum of hydrogen:
hf = 13.6 eV(1/nf2 - 1/ni2),  
1/λ = (13.6 eV(/hc))(1/nf2 - 1/ni2) = R(1/nf2 - 1/ni2).