Question

The correct order of ionic radii for the ions, P^3– , S^2– , Ca²⁺, K⁺ , Cl^– is : 

(1) P^3– > S^2– > Cl^– > K⁺ > Ca²⁺ 

(2) Cl^– > S^2– > P^3– > Ca²⁺ > K⁺ 

(3) P^3– > S^2– > Cl^– > Ca²⁺ > K⁺ 

(4) K⁺ > Ca²⁺ > P^3– > S^2– > Cl^-

Answer 1

Answer is (1) P^3– > S^2– > Cl^– > K⁺ > Ca²⁺ 

(Correct order of ionic radii) 

all the given species are isoelectronic species. 

In isoelectronic species size increases with increase of negative charge and size decreases with increase in positive charge.