John Dalton (1766- 1844)

 

Dalton built the atomic model called the atomic theory of matter. He stated that each type of matter is made of only one type of atom. He defined element as a group that each type of atom can be put in. Dalton concluded that every atom of a given element was identical.

Atoms could not be divided into smaller parts, and not created or destroyed. The name of his model was Billiard Ball Model. The Billiard ball model was called the Billiard Ball Model because you could not break down a billiard ball just like an atom could not be broken down. He figured out that there are small microscopic atoms.

He studied chemical reactions, he experimented with different mixtures of gases to identify how  the property of the individual gas affected the mixture of gases.

Discovered that atoms can be divisible by atomic reaction and not chemical reaction. When there is a chemical reaction, it's the atom being rearranged. Discovered that in a given element its mass and property are the same.