Question

why s2- has larger radius then cl-?

Answer 1

Both sulphide and chloride belongs to the third period and the general trend along the third period is that size decreases along the period. So the size of sulphur is larger than chlorine. Apart from this fact we also know that the size of an anion is larger than its parent atom due to inter electronic repulsion. As the repulsion is more in case of S^{2- than} Cl^{1-, _{therefore the size of}} S^2- is larger than Cl^1-.