During the formation of positive ions, valence electrons are removed. Periodic Trends in Atomic Properties Atomic Radii Radius of atom determined by dividing the bond distance between two identical atoms in half. Once radii of several atoms are known, can use them to calculate radii of other atoms in a molecule. Negative ions are always larger than parent atoms because of decreased pull per electron and greater electron repulsions. Ionization Energy Energy to remove an electron from an atom in the gas phase.
Large gaps indicate removal of electrons from full shells.