The energy of an electron in the 3rd orbit of H- atom ( in J ) is approximately.

Options

A. `-2.18xx10^(-18)`
B. `-2.42xx10^(-19)`
C. `-1.21xx10^(-19)`
D. `-3.63xx10^(-19)`

Answer

B

Explanation

For electron in 3rd orbit of H-atom.
Energy `=-(2pi^(2)mk^(2)e^(4))/(n^(2)h^(2))`
Substituting the standard values, we get Energy
`=-(-2xx((22)/(7))^(2)xx9.1xx10^(-31)xx(9xx10^(9))^(2)xx(1.6xx10^(-19))^(4))/((6.6xx10^(-34))^(2)xx(3)^(2))`
`=(-2xx3.14xx3.14xx9.1xx9xx9xx(1.6xx1.6)^(2)xx10^(-31+18-76))/(9xx6.6xx6.6xx10^(-68))`
`=-2.42xx10^(-19)" J"`