Question

magnesium oxide is a binary ionic compound from its formula MGO how do you know that mg is the metal

Answer 1

Answer is: because it is first.
Oxide is a chemical compound that contains at least one oxygen atom and one other element. In oxide oxidation number of oxygen is -2. So in magnesium oxide oxidation number of magnesium is +2 (metal form cation).
When writing molecular formulas, metal is written first (because positive oxidation number).

Answer 2

Answer:

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 .