Dalton's Atomic Theory

John Dalton a chemist that created a theory containing the basics of atoms that include ideas such as;

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.

Others have expanded on his theory which is what makes up the practices of chemistry in the modern era.