What type of reaction occurs when two elements combine to form a product?

When two elements combine to form a product, the reaction is classified as a synthesis reaction. In this type of reaction, simpler substances, such as individual elements or simpler compounds, react to form a more complex compound. The general form of a synthesis reaction can be represented as A + B → AB, where A and B are the reactants that come together to create the new product AB.

In the context of chemistry, synthesis reactions are foundational as they illustrate how elements interact to create new substances, building more complex molecules from simpler ones. This is a fundamental concept in chemical reactions, showcasing the principle of conservation of mass where the total mass of reactants equals the total mass of products.

Other types of reactions serve different purposes. For instance, decomposition reactions break down a compound into simpler substances; single replacement reactions involve one element displacing another in a compound; and double replacement reactions involve the exchange of components between two compounds. Each of these reactions operates under different mechanisms and principles, highlighting the diversity of chemical behavior.