Live practice

For an allowed set, (n=1,2,3,ldots); (l=0,1,ldots,n-1); (m_l=-l,ldots,0,ldots,+l); and (m_s=pmfrac{1}{2}).

(a) This set is not permissible because the principal quantum number cannot be zero.

(b) For (n=1), the only permitted value is (l=0). Also (m_l=0) and (m_s=-frac{1}{2}) are allowed. Hence this set is permissible.

(c) For (n=1), (l) must be 0. The value (l=1) is not allowed, so this set is not permissible.

(d) For (n=2), (l=1) is allowed; (m_l=0) lies between (-1) and (+1), and (m_s=-frac{1}{2}). Hence this set is permissible.

(e) For (n=3), the allowed values of (l) are 0, 1 and 2. Therefore (l=3) is not allowed, so this set is not permissible.

(f) For (n=3), (l=1), (m_l=0) and (m_s=+frac{1}{2}) are all allowed. Hence this set is permissible.

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