Which of the following elements has least number of electrons in its $M$ shell ?

Which of the following elements has least number of electrons in its $M$ shell ?
  1. $K$
  2. $Mn$
  3. $Ni$
  4. $Sc$

Solution

$ { }_{19} \mathrm{~K}=1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6, 4 s^1 $ Number of electrons in $M$ shell $(n=3)=8$

Asked in: AP EAMCET 2004

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