The correct arrangement for the ions in the increasing order of their radius is (KCET 2014) (a) Na ,Cl ,Ca (b) Ca ,K ,S (c) Na ,Al ,Be (d) Cl ,F ,S

Since, 2 2 Ca ,K ,S have same number of electrons. So they are isoelectronic ions. It is known that the ion having greater number of protons will be smaller in size. Thus, the increasing order of ionic radii is 2 2 Ca K S