CBSE Class 11-science Answered

In a mechanical picture, an electron may be considered to spin about an axis passing through it and so possesses spin angular momentum in addition to the orbital angular momentum.

The spin quantum number ‘S’ determines the magnitude of the spin angular momentum of an electron and can only have a value of ‘1/2’. The magnetic spin quantum number m_s determines the direction of the spin angular momentum of an electron and has values of ‘1/2’ or ‘-1/2’.An atomic orbital can contain a maximum of two electrons. The two values of m_s correspond to labels for the two electrons that can be accommodated in any one orbital. When two electrons occupy the same orbital, one possesses a value of m_s ‘1/2’ and the other m_s ‘-1/2’.We say that this corresponds to the two electrons having opposite spins.