Final answer:
The correct answer to the problem is A: Reactants: 2 Mg atoms, Product: 2 MgO molecules. In the reactants, there are a total of four atoms (two Mg atoms and two O atoms from one O₂ molecule), while in the product, there is an equal number of Mg and O atoms since the product consists of two MgO molecules.
Step-by-step explanation:
When analyzing the reaction 2 Mg + O₂ → 2 MgO, we can determine the number of atoms involved before and after the reaction occurs. Magnesium (Mg) is an element, meaning it is not a molecule but an individual atom in its most basic form. Oxygen (O₂), on the other hand, is a diatomic molecule, consisting of two oxygen atoms bonded together.
In the reactants, we have two magnesium atoms and one oxygen molecule which contains two oxygen atoms. So, regarding the reactants, there are a total of four atoms: two Mg atoms and two O atoms (from one O₂ molecule).
Looking at the products, each magnesium oxide (MgO) molecule consists of one magnesium atom and one oxygen atom. Since we have two MgO molecules as products, there are two Mg atoms and two O atoms in total on the product side as well. Therefore, the correct answer is A: Reactants: 2 Mg atoms, Product: 2 MgO molecules.