What term describes a substance in which the atoms of two or more elements are combined in fixed proportions?

What term describes a substance in which the atoms of two or more elements are combined in fixed proportions?

• A. Element
• B. Pure substance
• C. Compound
• D. Mixture

Answer: (C)

Two or more elements joined together in a specific, fixed ratio describes a compound. In a compound, atoms are held together by chemical bonds, so every sample has the same composition—like water, which always has two hydrogen atoms for every one oxygen atom. This fixed proportion and chemical bonding distinguish compounds from other substances. A pure substance could be either an element or a compound, but the phrase describes a substance formed from multiple elements in a set ratio, which is the defining feature of a compound. In contrast, a mixture is just a physical blend of substances without chemical bonding, and the amounts of each component can vary. An element, meanwhile, contains only one kind of atom.

Two or more elements joined together in a specific, fixed ratio describes a compound. In a compound, atoms are held together by chemical bonds, so every sample has the same composition—like water, which always has two hydrogen atoms for every one oxygen atom. This fixed proportion and chemical bonding distinguish compounds from other substances.

A pure substance could be either an element or a compound, but the phrase describes a substance formed from multiple elements in a set ratio, which is the defining feature of a compound. In contrast, a mixture is just a physical blend of substances without chemical bonding, and the amounts of each component can vary. An element, meanwhile, contains only one kind of atom.