In H atom, the electron is bound by Coulomb interaction and its three quantum numbers $n, l, m$ are related as $n=1,2,3,4, \ldots ; l=0,1,2, \ldots n-1 ; m=-l,-(l-1), . .0 . .,(l-$ $1), l$. The spin quantum number $s=1 / 2$ and $-1 / 2$. Thus, the maximum number of electrons that can occupy the first four shells $(n=1,2,3,4)$ are $2,8,18,32$, respectively. In artificial atoms (atomic clusters), where the electrons are bound by spherical harmonic oscillator potential, $n=0,1,2,3,4, .$. with $l=0,2,4,6, . . n$, for even $n$, and $l=1,3,5,7, . . n$, for odd $n$. The possible values of $m$ and $s$ remain the same as in the case of H atom. The filled shell configuration for this system for filling up to $n=1,2,3$ and 4 will respectively correspond to the electron numbers

• Correct answer
  A

  $8,20,40,70$
• B

  $6,18,38,68$
• C

  $6,12,20,30$
• D

  $2,8,18,32$

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