Ionisation energy of `He^+` is `19.6 xx 10^-18 J "atom"^(-1)`. The energy of the first stationary state `(n = 1)` of `Li^( 2 +)` is.

Options

A. `-2.2xx10^(-15)`J `"atom^(-1)`
B. `8.82xx10^(-17)" J atom"^(-1)`
C. `4.41xx10^(-16)" J atom"^(-1)`
D. `-4.41xx10^(-17)" J atom"^(-1)`

Answer

D

Explanation

`(I_(He^(+)))/(I_(Li^(2+)))=(Z_(1)^(2))/(Z_(2)^(2))`
`(19.6xx10^(-18))/(I_(Li^(2+)))=(4)/(9)`
`I_(Li^(2+))=(9)/(4)xx19.6xx10^(-18)=44.1xx10^(-18)`
`=4.41xx10^(-17)" J atom"^(-1)`
`E_(Li^(2+))=-4.41xx10^(-17)"J atom"^(-1)`.