Answer:
K+ < Cl- < S2- < P3-.
Explanation:
The electronic configuration of K is 2,8,8,1. So,K has 19 electrons.Hence,K+ will have 18 electrons.
Similarly,electronic configuration of P is 2,8,5. So,P has 15 electrons.Hence,P^3- will have 18 electrons .
Similarly,electronic configuration of S is 2,8,6. So, S has 16 electrons. Hence,S^2- will have 18 electrons.
Similarly,electronic configuration of Cl is 2,8,7. So,Cl has 17 electrons.Hence,Cl^ 1- will have 18 electrons .
As,all of these species are isoelectronic, so the smallest radius among these will be of that which possesses more amount of +ve charge on it.The reason is that a species having +ve charge on it will be effectively able to attract the outermost valence electrons to the nucleus.
Hence,the order of increasing order of radii is as follows:
K+ < Cl- < S2- < P3-.
