Question

The ionic radius of S2- ion is larger than that of Cl- ion. Why?

Answer 1

The radii of the ions depend on the force of attraction between the nucleus and the orbiting electrons .
The atomic number of sulphur is 16 and that of chlorine is 17 so here if it means that sulphur has 16 protons in it's outermost shell and chlorine has 17 protons in it's outermost shell . So if we add  2 more electrons to sulphur we get S2- ion and if we add one more electron to chlorine then it becomes Cl- ion
Here although chlorine and sulphur ions have same number of electrons they have different number of protons
The number of protons in sulphur < number of protons in chlorine
Hence the larger number of protons assures larger force of attraction which we can see in case of chlorine and if the number of protons is less then the attraction force is not much strong  (in case of sulphur)

Hence as the attractive force experienced by chlorine is greater than that sulphur electrons the radius of chlorine is less than than that of sulfur
Hence
The ionic radius of S2- ion is larger than that of Cl- ion



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