In 1803, an English scientist John Dalton (1766-1844) stated his theory in a lecture to the Royal Institution. The theory proposed a number of basic ideas:
1) All matter is made of atoms. Atoms are indivisible and indestructible.
2) All atoms of a given element are identical in mass and properties
3) Compounds are formed by a combination of two or more different kinds of atoms.
4) A chemical reaction is a rearrangement of atoms.