when atoms form ions, their radius generally changes. determine which statement best explains the change in the radius when a positive ion is formed. when atoms form ions, their radius generally changes. determine which statement best explains the change in the radius when a positive ion is formed. positive ions tend to have a larger radius than their parent neutral atom because electrons are gained in the outer energy level thus increasing the repulsion between the electrons. positive ions tend to have a smaller radius than their parent neutral atom because electrons are lost from the outer energy level thus reducing the repulsion between the electrons. positive ions tend to have a larger radius than their parent neutral atom because electrons are lost from the outer energy level which allows the inner electrons to expand. positive ions tend to have a smaller radius than their parent neutral atom because electrons are gained in the outer energy level increasing the attraction between the positive nuclear charge and the electrons.