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. `4.41 xx 10^(-16)J "atom"^(-1)`
B. `-4.41 xx 10^(-17)J "atom"^(-1)`
C. `-2.2 xx 10^(-15)J "atom"^(-1)`
D. `-8.83 xx 10^(-17)J "atom"^(-1)`

Answer

B

Explanation

`I.E =- E_(1), E_(n) prop (z^(2))/(n^(2)) rArr ((E_(1))_(He^(+)))/((E_(1))_(Li^(+2))) =((z_(He^(+)))^(2))/((z_(Li^(+2)))^(2))`