Question

an element 'X' react with oxygen to give 'XO' . given valency of 'X 'and it's number of electrons in outermost shell. ​

Answer 1

In my view X is a Calcium Ca

Has valency 2

And there are number of electrons in its valence shell therefore it losses two electrons

Answer 2

Since,

The compound formed conducts electricity, it should be ionic.

So,

The element X should have 2 valence electrons which it donates to oxygen to form XO.

Element X is a metal.

When element X reacts with chlorine, it forms $XCl_{2}$.

It donates 2 valence electrons to 2 chlorine atoms.