Question

In an element 'X', 3rd electron of 3rd shell is its last electron. In another element 'Y',7th electron of 3rd shell is its last electron. Then
(a)Identify 'X' and 'Y'.
(b)What will be the valency of Y?

Answer 1

(a) X = Aluminium & Y = Chlorine

(b) 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 Y is 1.