What results from the combination of atoms in a specific ratio?

The correct answer, a compound, is defined as a substance formed when two or more different types of atoms combine in a specific ratio through chemical bonds. Compounds have unique properties that are different from the individual elements that compose them. For example, water (H2O) is a compound made from two hydrogen atoms and one oxygen atom bonded together in a specific ratio. This chemical combination results in a new substance with distinct characteristics.

In contrast, mixtures consist of two or more substances that are physically combined but not chemically bonded, allowing each substance to retain its own properties. Solutions are a type of mixture where one substance is dissolved in another, typically involving liquids, while colloids are mixtures where fine particles are dispersed throughout another substance, but again, these do not involve a specific chemical combination. Therefore, a compound is the type of substance that results from the combination of atoms in a specific ratio, leading to the creation of a brand-new material.