Question

Which changes occur as a cadmium atom, Cd, becomes a cadmium ion, Cd2+?

Answer 1

The answer is (3). To form the cation (positive ion), Cd must lose negative charge, so two electrons are lost. This loss in electrons also increases the effective nuclear charge/ reduces electron shielding. In other words, with two less electrons to hold, the nucleus exerts a stronger attractive force on the remaining electrons, so the electron cloud is pulled closer to the nucleus. The radius therefore decreases.