Question

what is meant by spin quantum number and who introduced that?

Answer 1

the spin quantum numberis a quantum number that parameterizes the intrinsic angular momentum (or spin angular momentum, or simply spin) of a given particle. The spin quantum number is the fourth of a set of quantum numbers (the principal quantum number, the azimuthal quantum number, the magnetic quantum number, and the spin quantum number), which completely describe the quantum stateof an electron. It is designated by the letter s. It describes the energy, shape and orientation of orbitals. The name comes from a physical spinning (denoted by the letter s) about an axis that was proposed by Uhlenbeck and Goudsmit. However this simplistic picture was quickly realized to be physically impossible[1] and replaced by a more abstract quantum-mechanical description.

In 1925, five years before postulating the neutrino, Pauli introduced his Exclusion Principle. He showed that the various atomic spectra would make sense if the electron states in an atom are described by four quantum numbers and if each of these states is occupied by only one electron