Which of the following sequences correctly represents the decreasing order of ionic radii for the gi — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

In an isoelectronic series (here, all species have 18 electrons), the ionic radius is inversely proportional to the effective nuclear charge ($Z_{eff}$). As the atomic number ($Z$) increases ($S=16, Cl=17, K=19, Ca=20, Sc=21$), the nucleus attracts the same number of electrons more strongly, resulting in a continuous decrease in ionic size.