Classification of Elements and Periodicity in Properties - Result Question 20
####20. The correct order of the decreasing ionic radii among the following isoelectronic species are :
(a) $Ca^{2+}>K^{+}>S^{2-}>Cl^{-}$
(b) $Cl^{-}>S^{2-}>Ca^{2+}>K^{+}$
[2010]
(c) $S^{2-}>Cl^{-}>K^{+}>Ca^{2+}$
(d) $K^{+}>Ca^{2+}>Cl^{-}>S^{2-}$
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Solution:
(c) Among the isoelectronic species, size increases with the increase in negative charge. Thus $S^{2-}$ has the highest negative charge and hence largest in size followed by $Cl^{-}, K^{+}$and $Ca^{2+}$.
