Dalton's Atomic Theory

The Greek philosopher Democritus first suggested the existence of the atom but it took almost two thousand years before atomic theory gained some support as a resulted of work by John Dalton (1766-1844), a self taught scientist living in Manchester, England.
Dalton's Atomic Theory stated
1) All matter is made of atoms. Atoms are indivisible and indestructible.
2) All atoms of a element are identical in mass and properties.
3) Compounds are formed by combinations of different kinds of atoms.
4) A chemical reaction is a rearrangement of atoms.
Dalton's theory was a major advance, and provided a big impetus to find the elements. Many heretofore unexplained chemical phenomena were quickly explained by Dalton with his theory. Dalton's theory quickly became the theoretical foundation in chemistry.