Question

An electron revolves round a nucleus of charge Ze. In order to excite the electron from the `n=20` to `n=3`, the energy required is `47.2 eV`. Z is equal to
A. 3
B. 4
C. 5
D. 2

Answer 1

Correct Answer - C
`Z^(2)[(13.6)/(4)-(13.6)/(9)]=47.2 `
` :. " " Z=5`