What is the energy of He electron in first orbit ?

Options

A. `40.8 eV`
B. `-27.2 eV`
C. `-54.4 eV`
D. `-13.6 eV`

Answer

C

Explanation

For hydrogen like atoms like `He^(+), Li^(+)` atc. The energy in an `n^(th)` orbit is given by
`E_(n)=(-Z^(2)13.6)/(n^(2))eV`
For `He^(+), Z = 2`
`therefore E_(1)=(-(2)^(2)13.6)/((1)^(2))eV = -54.4 eV`