**(1) Magnetic quantum number:**

- It is denoted by the letter m
_{1} It takes integral values ranging from –I to +I through 0. i.e. if l = 1; m = -1, 0 and +1.
- The Zeeman Effect (the splitting of spectral lines in a magnetic field) provides the experimental justification for this quantum number.
- The magnitude of the angular momentum is determined by the quantum number l while its direction is given by magnetic quantum number

**(2) Spin quantum number:**

- The spin quantum number represents the spin of the electron and is denoted by the letter ‘m
_{s} ‘.
- The electron in an atom revolves not only around the nucleus but also spins. It is usual to write this as electron spins about its own axis either in a clockwise direction or in anti – clockwise direction.
- Corresponding to the clockwise and anti – clockwise spinning of the electron, maximum two values are possible for this quantum number.
- The values of ‘m
_{s} ‘ is equal to \(-\frac{1}{2}\) and \(+\frac{1}{2}\).