Question

If energy required to remove one of the two electrons from He atom is 29.5 eV, then what is the value of energy required to convert a helium atom into particle?

Answer 1

The helium atom has two electrons bound to a nucleus with charge Z = 2. The successive removal of the two electrons can be written as
He → He+ + e- → He++ + 2e-
The minimum energy required to remove the first electron from helium is given as 29.5 eV. The second ionization energy can be calculated exactly since He+ is a hydrogenlike ion. The second ionization energy of He is the ionization energy of He+.
- E1s (He+) = Z2RH/(2n2)
where RH = 2.178 x 10-18 J (convert into eV).
It can be calculated to be 54.4 eV.
$=54.4eV$