Electron Spin and the Pauli Exclusion Principle 4.Spin quantum number ms: N S Electrons actually spin around itself. 1 m,=士 2 S N Copyright2009 Pearson Prentice Hall,Inc.4. Spin quantum number ms: Electrons actually spin around itself. Electron Spin and the Pauli Exclusion Principle 1 2 m s = ± spin around itself