the atomic theory
Early Atomic Theory
The atomic theory, which holds that matter is composed of tiny, indivisible particles in constant motion, was proposed in the 5th cent. B.C. by the Greek philosophers Leucippus and Democritus. However, Aristotle did not accept the theory, and it was ignored for many centuries.
Modern Atomic Theory
The modern atomic theory was published by John Dalton in 1808. He held that all the atoms of an element are of exactly the same size and weight, and also stated that atoms of the elements unite chemically in simple numerical ratios to form compounds. The best evidence for his theory was the experimentally verified the "law of simple multiple proportions" , which gives a relationship between the weights of two elements that combine to form different compounds.
