Question

If elements with principal quantum number $n>4$ were not allowed in nature, the number of possible elements would have been

• A. $32$
• B. $60$
• C. $18$
• D. $4$

Answer 1

The correct option is B $60$

The no. of electrons in $n^{th}$ shell is $2n^2$.
${\sum }_1^{4}2n^2=60$