(i) Element A belongs to group I of the Periodic Table. So, it has I valence electron and it forms unipositive ion by losing its valence electron. Hence, A is a metal.
(ii) This is because element C is in third period while element ts is in second period. We know,that the atomic size increases down the group and decreases along a period.
(iii) Element B is in 2nd period and 3rd group hence it has 3 valence electrons. It loses 3 electrons to achieve nearest inert gas configuration. So, its valency is 3.
