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. 64
D. 4

Answer

B

Explanation

`N = Sigma 2 n^(2)`
`N = 2 (1^(2) + 2^(2) +3^(2) +4^(2)) = 60`