The radius of hydrogen atom in the ground state is `5.3 xx 10^(-11)` m. When struck by an electron, its radius is found to be `21.2 xx 10^(-11) m`. The principal quantum number of the final state will be

Options

A. 1
B. 2
C. 3
D. 4

Answer

B

Explanation

`r_(n) prop n^(2)`
`(n^(2)/(n^(2)) = (21.2 xx 10^(-11))/(5.3 xx 10^(-11)))` or `(n^(2)/(n^(2))) = 4`
or `(n^(2)/(1^(2))) = 4` or `n = 2`