Which quantum number divides shells into orbitals?

The quantum number that divides shells into orbitals is the azimuthal quantum number. This number determines the shape of the orbital and can have values ranging from 0 to n-1, where n is the principal quantum number. Each value of the azimuthal quantum number corresponds to a different subshell, which in turn determines the shape of the orbital. For example, an azimuthal quantum number of 0 corresponds to an s subshell, which has a spherical shape, while an azimuthal quantum number of 1 corresponds to a p subshell, which has a dumbbell shape with two lobes. So, the azimuthal quantum number plays a crucial role in dividing shells into orbitals.