the history of the atom

Democritus

440 BCE

First proposed the existence of an ultimate particle. Used the word "atomos" to describe this particle.

Aristotle

340 BCE

was a proponent of the continuum. He believed in the four elements of air, earth, water and fire. Aristotle felt that regardless of the number of times you cut a form of matter in half, you would always have a smaller piece of that matter. This view held sway for 2000 years primarily because Aristotle was the tutor of Alexander the Great.

Johann Becher and Georg Stahl

Period: Jan 1, 1635 to Jan 1, 1734

developed the Phlogiston theory which dominated chemistry between 1670 and 1790. Basically, when something burned, it lost phlogiston to the air (after all, you could see the phlogiston leaving) A problem with the theory was that burning of metals resulted in an increase in the mass. This problem was solved by assigning negative mass to phlogiston.