If elements with principal quantum number `ngt 4` were not allowed in nature, the number of possible elements would be:

Options

A. 20
B. 40
C. 60
D. 70

Answer

C

Explanation

The maximum number of electrons in any orbit of number n is `2n^2` . As n gt 4 is not allowed , the maximum number of electrons that can be accommodated in the first four orbits is equal to
`2(1)^2 + 2(2)^2 + 2(3)^2 + 2(4)^2 = 2 + 8 + 18 + 32 = 60`
`therefore` The number of possible elements = 60