1. In quantum mechanics, the azimuthal quantum number ℓ is a quantum number for an atomic orbital that determines its orbital angular momentum and describes aspects of the angular shape of the orbital. The azimuthal quantum number is the second of a set of quantum numbers that describe the unique quantum state of an electron (the others being the principal quantum number n, the magnetic quantum number mℓ, and the spin quantum number ms). For a given value of the principal quantum number n (electron shell), the possible values of ℓ are the integers from 0 to n − 1. For instance, the n = 1 shell has only orbitals with ℓ = 0 {\displaystyle \ell =0} , and the n = 2 shell has only orbitals with ℓ = 0 {\displaystyle \ell =0} , and ℓ = 1 {\displaystyle \ell =1} . For a given value of the azimuthal quantum number ℓ, the possible... from wikipedia.org