jan 1, 1808 - Dalton

Description:

Discovered that Atoms cannot be separated any further.
Discovered that Atoms cannot be created or destroyed in a chemical reaction
Discovered that Atoms of an element are all identical in mass, chemical properties, etc.
Discovered Atoms of different elements have different masses and chemical properties.
Discovered the relative ratio of atoms in a compound is consistent.
Dalton's Atom was not detailed, but simply a tiny round circle.