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.

Apotassium atom has 4 electrons in valance shell while potassium ion has 3 electrons in a electron shell. a k ion has one fewer electrons than k atom. that is  why the radius of a potassium atom is larger than the radius of the potassium ion in the ground state.

Spontaneity tell us the direction of the reaction, but not how fast it goes. gibbs free energy brings together enthalpy, entropy and temperature in one easy formula. g = h - ts. and, finally the sign of delta g is always negative for a spontaneous reaction.