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.
A 1,2-ethanediol has an ethane structure consisting of two Carbon atoms with a hydrogen from each carbon substituted by a hydroxyl group. This makes it a 1,2-diol.
