Democritus stated that all matter is composed of particles, naming these particles atoms derived from the Greek word Atomos meaning invisible. Therefore he sparked the initial idea of what an atom is.
Dalton made a breakthrough in the theory of the atom since Democritus' descovery. Dalton's atomic theory stated that:
1. All matter is made from hard, invisible particles (atoms)
2. Atoms of the same elements are identical and atoms of different elements are different making each element unique.
3. Elements cannot be made or destroyed and cannot be changed to a different element during a chemical reaction.
4. A chemical reaction is when atoms are rearranged, changing the way they are joined.
5. When atoms are combined in specific ratio, compounds are formed.