What is the quantum number for angular momentum that labels the subshells?
Quantum numbers are a set of four numbers used to described the energy levels of electrons in an atom. The first number is called the principle quantum number and gives the shell number of the electron. The second number is called the azimuthal quantum number that gives the subshell of the electron. The third number is the magnetic quantum number that gives the specific orbital of the subshell for the electron. The fourth number is the spin of the electron.
I think you are looking for the third number (magnetic) that labels the different subshells for electrons. There are four major subshells: s, p, d, and f. The s orbitals are spherically shaped, p orbitals are "dumbbell" shaped, d orbitals have four opposing lobes on the same plane, and f orbitals with more complex shapes. For any given subshell, there is 1 s orbital, 3 p orbitals, 5 d orbitals, and 7 f orbitals.