Question

The ionization energies of the alkali metals (that is, the lowest energy required to remove one outer electron when the atom is in its ground state) are about 4 or 5 ev, while those of the noble gases are in the range from 11 to 25 ev . Why is there a difference?

Short answer

Electron remove from completely filled orbit required more energy as comparison of not completely filled orbit.

Step-by-step solution

Definition of metal

The term metal may be defined as the element have property of loss of electron.

Explain the reason

Electron remove from completely filled orbit required more energy as comparison of not completely filled orbit.

Hence, the ionization energies of the alkali metals (that is, the lowest energy required to remove one outer electron when the atom is in its ground state) are about 4 or 5 ev, while those of the noble gases are in the range from 11 to 25 ev