Write the chemical equation for: magnesium+oxygen -> magnesium oxide.

Magnesium metal reacts with oxygen gas, when it burns, to form magnesium oxide. This reaction can be written as:

However, this is not a balanced chemical equation as oxygen atoms are not equal on the reactant and product side of the equation. The well balanced chemical equation for this reaction is:

Magnesium is a group 2 element and being a metal readily loses 2 electrons to form the magnesium ion, Mg2+. Similarly, oxygen is a non metal and readily accepts 2 electrons to form the oxide ion, O2-. Thus, oxygen accepts the 2 electrons donated by the magnesium atom and both these ions achieve a fully-filled electronic configuration. The resultant product is magnesium oxide.

Hope this helps.