(a) The electropositive character of the elements increases on going down in a group of the periodic table.
(b) (i) In a group, all the elements will have the same valency because all the electrons have the same number of electrons in their outermost shell.
(ii) In a period, different elements have different valencies. On moving from left to right in a period, the valency of the elements increases from 1 to 4 and then decreases to 0.