Final answer:
Magnesium reacts with oxygen in a highly exothermic combination reaction to form magnesium oxide, with magnesium being oxidized. Energy is emitted as light and heat, and a flame is needed to initiate the reaction. The reaction equation given is correctly balanced.
Step-by-step explanation:
For the reaction Mg(s) + O2(g) → MgO(s), the magnesium (Mg) must be placed into a flame to start this reaction. This is because the reaction is highly exothermic, where energy is given off as light and heat, making it a very dramatic demonstration. Essentially, this process is a combination reaction where magnesium combines with oxygen to form magnesium oxide (MgO).
The chemical equation provided, 2Mg(s) + O2(g) → 2MgO(s), is indeed a balanced reaction, making option C valid. Two atoms of magnesium react with one molecule of oxygen (which consists of two oxygen atoms) to produce two units of magnesium oxide. During this reaction, magnesium is oxidized, meaning that it loses electrons to oxygen (which is reduced by gaining those electrons), making option D correct.
Although magnesium does react with oxygen, it typically requires a flame to initiate the reaction because it must reach a certain temperature to start. Therefore, after the initial ignition, no additional heat is necessary since the exothermic nature of the reaction sustains the flame, which may lead to the misconception in option E that no additional heat is required to maintain the reaction.