How is a radioactive element different from a stable element?

Iron(iii) ions, fe3+ , react with thiocyanate ions, scn- , in a reversible reaction to form a red solution. which changes to the equilibrium will make the solution go red? i. increasing the temperature ii. adding fecl3 iii. adding a catalyst a. i and ii only b. i and iii only c. ii and iii only d. i, ii and iii