Who put forward the first atomic theory?

The development of quantum theory was arguably many centuries in the making. As early as the 5th Century B.C., the Greek philosophers Democritus and Leucippus first put forward the idea that everything around us was made of tiny indivisible pieces called atoms scattered in an infinite void. read more

4) A chemical reaction is a rearrangement of atoms. Dalton's atomic theory is correct in essence with a few exceptionsto his rules: 1) Atoms are the smallest unit of mater that retain the physicaland chemical properties of an element, however, they are divisibleby non-chemical means. read more

The first practical atomic theory was put forward by the English chemist and physicist John Dalton during the years 1803 to 1808. The background for this theory was the law of conservation of mass and the law of constant proportions. read more