What is the atomic theory timeline

A Timeline on Atomic Structure. 400 B. C. Democritus' atomic theory posited that all matter is made up small indestructible units he called atoms ... 1803 John Dalton proposed that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together.

Atomic theory is the scientific theory of the nature of matter. The theory states that matter is made up of small particles called atoms. Prior to this theory, matter was thought to be able to be divided into any small quantity. The word atom is derived from the Greek atmos, meaning indivisible.