Question

Ionisation energy of helium is that of hydrogen.

• A. more than
• B. less than
• C. equal to

Answer 1

The correct option is A more than

The electronic configuration of Helium is -

K

2

and Hydrogen is -

K

1

Helium has higher nuclear charge and smaller atomic radius than hydrogen. Thus, the magnitude of the force acting on each electron of helium is more. So, a higher amount of energy is required to knock out its valence electron. Hence, the ionisation energy of helium is more than that of hydrogen.