# What quantum numbers are needed to specify a hydrogenic atomic orbital?

Oct 31, 2016

You need three quantum numbers, $n , l$ and ${m}_{l}$ to completely specify an orbital.

#### Explanation:

The principal quantum number, $n$, specifies the energy and the relative size of the orbital.

The azimuthal quantum number, $l$, specifies the shape of the orbital.

The magnetic quantum number, ${m}_{l}$, specifies the orientation of the orbital in space.

For example, each of the three 2p orbitals has a different set of $n , l$ and ${m}_{l}$.