Q3 / 200 · Manipal (MET) 2013 · Chemistry

What are the four quantum numbers of 19 th electron in $\mathrm{Sc}(Z=21)$ ?

  • Correct answer
    A
    $n=4, l=0, m=0, m_s=+\frac{1}{2}$
  • B
    $n=3, I=1, m=-1, m_s=+\frac{1}{2}$
  • C
    $n=4, l=1, m=+1, m_s=-\frac{1}{2}$
  • D
    $n=3, l=2, m=+2, m_s=-\frac{1}{2}$

Solution

Sc $(21)=1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 3 d^1 s^2$ 19th electron goes into 4 s Hence, $n=4$ $l=0$, $m=0, \quad m_s=+\frac{1}{2}$

Hence, the correct answer is option: 'A'.

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