Question

X and Y have atomic numbers 16 and 12 respectively. Write the formula of a compound formed by X and Y.

Answer 1

X-->2,8,2

Y-->2,8,6

X belongs to 3rd period - 2nd group.

So the element is Mg

Y belongs to 3rd period - 6th group.

So the element is Sulphur.

{no. of electrons in the outer most shell determines the group and total no.of shells determine the period.}

They form ionic bonds because they complete their octet by transfring electrons.
therefore they exist in the form of XY by completing their octet (ionic bond).