Question

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

• A. 60
• B. 32
• C. 4
• D. 64

Answer 1

Answer: (A)

The maximum number of electrons in an orbit are $2n^2$. If
$n>4$, is not allowed, then the number of maximum electrons
that can be in first four orbit are :
$2(1{)}^2+2(2{)}^2+2(3{)}^2+2(4{)}^2=2+8+18+32=60$
Therefore, possible e' ments can be 60.