If in nature they may not be an element for which the principle quantum number `n gt 4`, then the total possible number of elements will be

Answer

`60`

Explanation

Upto quantum number 4, an atom has K,L,M and N shell. In any shell, max. no. of electrons is `2n^(2)`. Therefore,
in K shell, max no. of electrons `=2(1)^(2)=2`
in L shell, max no. of electrons `=2(2)^(2)=8`
in M shell, max no. of electrons `=2(3)^(2)=18`
in N shell, max no. of electrons `=2(4)^(2)=32` Total max. no. of electrons in these shells
`=2+8+18+32=60`
Hence, number of elements would be 60