Which statement is a postulate of Dalton's atomic theory?

• A. Atoms are indivisible
• B. Atoms of the same element are identical
• C. All things are made of atoms
• D. Compounds are formed by combining elements in fixed ratios

Answer: (C)

Matter is made of tiny, discrete particles called atoms. This idea is the foundation of Dalton's theory: everything around us is built from these atoms, and chemical changes involve rearranging them to form new substances rather than creating new matter from nothing or destroying atoms. Saying that all things are made of atoms captures that universal building-block concept the theory rests on. (Keep in mind that later science showed atoms can be subdivided and that atoms of the same element aren’t always identical, but the core postulate being tested is that everything is composed of atoms.)