Question 7: Why ₂He⁴ has larger ionization energy than H?

ANSWER

Electrons are being removed from the same orbits in the case of helium and hydrogen. Therefore, apparently, both should have the same ionization energy. However, the ionization energy of helium is much larger than hydrogen. It is because the nucleus of helium has two protons attracting the electron as compared to one in the hydrogen.

Thus it is because of the more Coulomb force between the nucleus and electrons of the helium atom which require more energy of ionization than hydrogen.