How did John Dalton's atomic theory differ from the earlier ideas of Democritus?

John Dalton’s atomic theory differed significantly from the earlier ideas of the Greek philosopher Democritus primarily in its scientific foundation and its application to chemistry.

While Democritus’s atomic philosophy was based on reason and mathematics rather than empirical evidence, John Dalton converted these concepts into a scientific theory between 1803 and 1808 by incorporating experimental observations, measurements, and tests.12

Key differences include:

• Experimental Basis: Unlike the Greek theory, which lacked scientific value because it was not based on experiments, Dalton’s model was built upon the law of conservation of mass, the law of definite proportions, and the law of multiple proportions.2
• Chemical Elements: Dalton linked atoms directly to chemical elements as defined by Antoine-Laurent Lavoisier. He proposed that there are as many different kinds of atoms as there are chemical elements, and that atoms of a specific element are identical in mass, shape, and size.23
• Quantitative Focus: Dalton emphasized determining the relative weights of atoms and the specific ratios in which they combine to form compounds, providing a physical picture of chemical reactions that the ancient Greeks did not possess.23

Despite these advancements, Dalton maintained the Democritean view that atoms are indivisible, indestructible, and retain their identity during chemical reactions.23