Atoms that only have one electron are called hydrogenoids. They are hydrogenoids atoms: H, He + , Li 2+ , Be 3+ .

Hydrogen atoms present a factorable wave function in a radial part and a spherical harmonic, which has the form:


where n,l,m are the quantum numbers that make the wave function acceptable.

The energy of a hydrogen atom is given by the expression:


As can be seen, the energy depends exclusively on the principal quantum number, n.