The energy of an electron in the first orbit of the hydrogen atom is `-2.18xx10^(-18)`J/atom. What is the thrid ionisation energy of `Li^(2+)` ion?

Options

A. `8.72xx10^(-18)J`
B. `4.36xx10^(-18)J`
C. `+19.62xx10^(-18)J`
D. `6.54xx10^(-18)J`

Answer

C

Explanation

III. Ionisation energy of `Li^(+2)`
`=-(z^(2))/(n^(2))E_(1)H(z=3,n=1)`
`=-(z^(2)xx-2.18xx10^(-18))/(n^(2))`J/species
`=-(-9xx2.18xx10^(-18))`
`=19.62xx10^(-18)J`