460 B.C. Greek philosopher develops the idea of the atom
Democritus asks himself: "How many times can you break a piece of matter in half until you can break no more?" He concluded that it ended at some point, the smallest possible bit of matter.
Antoine Laurent Lavoisier
Discovered the law of conservation of mass
Discovered the law of definite proportions
John Dalton proposes his atomic theory. Dalton's atomic theory is the theory that all matter is made of atoms. Atoms are indivisible and indestructible.
Thomson discovered the electron
Robert A. Milikan
Measured the charge of the electron
Known for his remarkable orbital theory of the atom in his famous Gold Foil experiment. He is also known as the “father of nuclear physics".
developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level to another.