If electron with principal quantum number `n gt 4` were not allowed in nature , the number of possible element would be

Options

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

Answer

B

Explanation

If all the elements having `ngt4` are removed the number of elements that will be present in the periodic table are calculated as
n=1 represents K shell and the number of elements having K shell =2 [ in accoredance with `2n^(2)`]
n=2 , repreents L shell and the number of elements having L shell =8
n=3 represent M shell and the number of elements having M shell =18
n=4 represents N shell and the number of elements having N shell =32
So, the number of elelments of elements having `nlt5` are
`" " 2+8+18+32=60`