An element X with atomic number 12 forms a compound with element Y with atomic number 17. The formula of the compound formed is (A) XY (B) XY₂(C) X₂Y (D) X₂Y₃

Correct Answer: (B) XY2

Explanation: Electronic configuration of X= 2,8,2, hence, it has a valency of X = 2

Electronic configuration of Y =2,8,1, hence, it has a valency of Y=1. On crossing their valency and notating as subscript we get the formula as XY₂.