Ionic radius is inversely proportional to charge present on metal respectively. In transition metal series, ionic radius will decreases gradually from Sc to Mn and constant in middle from Fe to Co and again increase from Ni to Zn. Hence, Sc3+>V5+>Mn7+ Greater the oxidation state, lesser will be the ionic radii. S2− acquire very high charge in it. It increases our ionic radii than K+. Therefore, S2− is very big in size. Hence, correct order of ionic radii is S2−>K+>Sc3+>V5+>Mn7+