In the year 1925 two physicists, Samuel Goudsmit and George Uhlenbeck proposed the concept of Electron Spin.
The spin quantum number (ms) describes the angular momentum (or spin) of an electron about an axis.
Reference Source:
[1] Wikipedia Contributors. Spin quantum number. Wikipedia. Published November 11, 2021. Accessed December 9, 2021. https://en.wikipedia.org/wiki/Spin_quantum_number.
[2] Wikipedia Contributors. Samuel Goudsmit. Wikipedia. Published December 7, 2021. Accessed December 9, 2021. https://en.wikipedia.org/wiki/Samuel_Goudsmit.
[3] Wikipedia Contributors. George Uhlenbeck. Wikipedia. Published July 14, 2021. Accessed December 9, 2021. https://en.wikipedia.org/wiki/George_Uhlenbeck.