An element 'X' belongs to 3rd period and group 17 of the periodic table. State its (i) electronic configuration, (ii) valency. Justify your answer with reasoning.

(i) Since element X' belongs to 3rd period, it means that the element X has three shells. Also, it belongs to group 17 which means that it has 7 valence electrons as valence electrons=17−10=7. So, the electronic configuration of the element X is 2, 8, 7
(ii) Since the outermost shell has 7 electrons in its outermost shell means that it requires one more electron to acquire noble gas configuration. So, the valency of X is 1.