The decrease in ionic radius within a series occurs because, as the atomic number increases, a new electron enters a d orbital for each unit increase in nuclear charge. The less effective shielding of d electrons leads to increased electrostatic attraction, causing a decrease in the ionic radius.
Why do ions of the same charge in a given series show a progressive decrease in radius with increasing atomic number?
Share
Ions of the same charge in a given series show a progressive decrease in radius with increasing atomic number due to the imperfect shielding of electrons in the same set of orbitals. As electrons are added, the nuclear charge increases, but the shielding effect of inner electrons is less effective in d orbitals. This results in a net increase in the electrostatic attraction between the nucleus and the outermost electrons, leading to a decrease in ionic radius. While the variation is small within a series, the imperfect shielding contributes to the observed trend of decreasing ionic radius with increasing atomic number in a given series of transition elements.