(i) Metals lie on the left-hand side of the Periodic table whereas non-metals are found on the right-hand side. The element A is in group 17. Group 17 is on the right side of the Periodic table. Thus, element A is a nonmetal
(called halogen).
(ii) The chemical reactivity of non-metals decreases on going down in a group. In group 17, the chemical reactivity decreases on going down in a group. So, element C is less reactive than A.
(iii) The atomic size decreases in moving from left to right along a period. So, atom C will be smaller in size than B.
(iv) The element A of group 17 has 7 valence electrons. So, it will gain one electron to form a negatively charged ion (A–). The negatively charged ion is called an anion. So, element A will form an anion.