The angular momentum quantum number , l , also called the azimuthal quantum number , describes the shape of an electron orbital. Each azimuthal quantum number has an associated subshell, s , p , d , or f , and identifying which subshells are present will predict the shape and behavior of an atom. Periodic table electron configurations Electron configurations of the elements data page. The first three are a little bit weird. It only takes a few minutes to setup and you can cancel any time. Valence electron Core electron.