Final answer:
John Dalton was not the first person to propose that matter is composed of smaller particles; that distinction goes to the ancient Greek philosophers Leucippus and Democritus. However, Dalton was the first to provide quantitative measurements supporting this theory, and his ideas form a significant part of our current understanding of atomic structure.
Step-by-step explanation:
While John Dalton did contribute significantly to our understanding of atomic theory, he was not the first to propose that matter is composed of smaller particles. The idea originated with the ancient Greek philosophers Leucippus and Democritus in the 5th century BCE, who proposed that all matter was composed of indivisible particles they named 'atomos'. However, their ideas were philosophical and not based on experimental evidence.
It was John Dalton, a British schoolteacher, who, in the early 19th century, provided the first quantitative measurements to support the atomic hypothesis. Dalton's atomic theory proposed that all matter is composed of atoms, that each element has distinctive types of atoms, and that these atoms can combine in fixed ratios to form compounds.
The theories of Dalton and the early Greek philosophers form the foundational concepts of modern chemistry, making them pivotal figures in science.
Learn more about Dalton's Atomic Theory