An element X (ato

(a) Since the element X has atomic number = 17. So, its electronic configuration will be 2, 8 and 7

It has 7 electrons in its outermost shell and therefore it belongs to the 10+7 th group i.e. group 17. Moreover, it has three electronic shells in total. So, it belongs to period 3.

The atomic number of element Y = 20

The electronic configuration of element Y= 2, 8, 8, 2

Now, element Y has 2 electrons in its outermost shell. So, the group number of element Y = 2. It has 4 electron shells. So, it belongs to period 4.

(b) Valency of element ‘X’ is 1

valency of element ‘Y’ is 2

‘X’ is a non metal and ‘Y’ is a metal. So, X and Y will form an ionic bond.

So, the compound formed is: YX₂