Question

(a) An element X has mass number 40 and contains 21 neutrons in its atom. To which group of the periodic table does it belong ?
(b) The element X forms a compound X2Y. Suggest an element that Y might be and give reasons for your choice.

Lakhmir Singh Chemistry Class 10

Answer 1

a) it belongs to group no 1
b. Y might be oxygen coz Frm the above mentioned formula X2Y it is clear that Y has valency 2

Answer 2

Answer:a)the proton no.=40-21=19

E.C=2,8,8,1

Therefore the valancy is 1 so it belong to group 1

b)it can be oxygen, sulphur or any any metal of group 16 b'coz its clear that the valancy of the element Y is 2

Explanation:X Y

1 × 2

X2Y........

Hope its clear......

And HELPED YOU.....