Second Quantum Number Definition

The second quantum number describes the shape of an electron's orbit.
The second quantum number describes the shape of an electron's orbit. PASIEKA / Getty Images

The second quantum number, ℓ, is the quantum number associated with the angular momentum of an atomic electron. The second quantum number determines the shape of the electron's orbital. When the second quantum number is combined with the principal, magnetic, and spin quantum numbers, an electron in an atom is described completely.

Also Known As: azimuthal quantum number, angular momentum quantum number

Examples: A p orbital is associated with a second quantum number equal to 1.