Dalton's Atomic Theory John Dalton in 1808 put forward theory known as Dalton's atomic theory The main points of this theory are: (1) Matter is made up of extremely small indivisible particles called atoms. (2) Atoms of the same element are identical in all respect i.e. shape, size and mass. (3) Atoms of different elements have different masses, sizes and also … [Read more...] about Dalton’s Atomic theory