It the 1st ionisation energy of H atom is 13.6 eV, then the 2nd ionisation energy of the atom is-

Options

A. 27.2 eV
B. 40.8 eV
C. 54.4 eV
D. 108.8 eV

Answer

C

Explanation

First ionisation energy of H-atom is calculated as:
`(2pi^(2)mZ^(2)e^(4))/(h^(2))((1)/(n_(1)^(2))-(1)/(n_(2)^(2)))=13.6eV" "[n_(1)=1 and n_(2)=oo]`
`therefore`Second ionisation energy of He atom is
`=13.6xxZ^(2)eV=13.6xx2^(2)eV=54.4eV`