Explain, in terms of electrons, why the radius of a potassium atom is larger than the radius of the potassium ion in the ground state.

Because the potassium atom has 19 electrons and there is four layers of electrons as 2, 8, 8, 1. And for potassium ion, there is 18 electrons. It has there layers of electrons as 2, 8, 8. So the radius of potassium atom is larger than potassium ion.