According to formula, magnesium gives electron forming a cation which is the property of metals according to periodic table.
Explanation:
Mg has a valency of two electrons which means it has two electron in the valence shell. It gives two electrons to an oxygen atom which becomes a anion.
They form two ionic bond forming MgO.
And the atoms of valency two are present in 2nd column which contains metals.
Hence from formula, it can be known that Mg is a metal.
