This reaction is classified as a combination reaction. In a combination reaction, two or more reactants combine to form a single product. Here, magnesium (Mg) and oxygen (O₂) are coming together to form magnesium oxide (MgO).
To break it down further:
- Reactants: Magnesium and oxygen
- Product: Magnesium oxide
Since there are two elements combining to create one compound, it clearly falls under the category of a combination reaction. None of the other options—decomposition, single replacement, or double replacement—apply here, as they involve different processes of breaking down compounds or exchanging elements between compounds.