Final answer:
The product when magnesium is fully burned in oxygen is magnesium oxide (MgO), a white powder resulting from a vigorous reaction that also releases a bright white flame.
Step-by-step explanation:
When magnesium is fully burned in oxygen, the product is magnesium oxide (MgO). This process is an oxidation-reduction reaction where magnesium metal is oxidized, losing electrons to the oxygen atoms. As the magnesium burns in the presence of oxygen, it reacts vigorously, releasing a bright white flame and heat, ultimately forming a white crumbly powder known as magnesium oxide.
The reaction of magnesium with oxygen is represented by the balanced chemical equation: 2Mg(s) + O₂(g) → 2MgO(s). The potent reducing power of magnesium makes it ideal for preparing some metals from their oxides due to its high affinity for oxygen. However, this same reaction of burning magnesium with carbon dioxide will not produce the intended fire-extinguishing effect; instead, it will result in the formation of magnesium oxide and elemental carbon, as evidenced by the reaction: 2Mg(s) + CO₂(g) → 2MgO(s) + C(s).