Spin Quantum Number Definition

The spin quantum number is the fourth quantum number, denoted by  s or ms. The spin quantum number indicates the orientation of the intrinsic angular momentum of an electron in an atom. It describes the quantum state of an electron, including its energy, orbital shape, and orbital orientation. The only possible values of a spin quantum number are  ½ or - ½ (sometimes referred to as spin up and spin down). The value of spin is a quantum state, not something so easily understood as the direction in which an electron spins! Sources Atkins, P.; de Paula, J. (2006). Physical Chemistry (8th ed.). W. H. Freeman. ISBN 0-7167-8759-8.Bertolotti, Mario (2004). The History of the Laser. CRC Press. pp. 150–153.Merzbacher, E. (1998). Quantum Mechanics (3rd ed.). John Wiley. p.430-1 ISBN 0-471-88702-1.