History of the Atom

Democritus Theory

460

He made the discovery that the smallest piece of any matter is an atom.Democritus came to this conculsion by his Proposed question:If you break a piece of matter,how many breaks can you make before it can not be broken any furthur.

Dalton

Mar 1, 1800

Dalton made the dicovery that all matter is made up of atoms. Perroming experiments with chemiclas that showed matter had lump particles,called atoms, led him to this discovery.

Thomson

Mar 1, 1897

Thomson made the discovery of the presence of the electron;he knew that electrons had a negative charge,so matter must have a positive charge. His idea of the atomic structure is a sphere full of elctrically positive substances mixed with negative electrons.Thomson used his rasin in the pudding model.

Rutherford

Mar 3, 1911

Rutherford followed Thomson's model,but discarded the plum pudding because he proved that the only way the alpha particles could be deflected backwards was if most of the mass was concentrated in a nucleus.He used the gold foil experiment to make his discovery to show that there would be very little to deflect the alpha particles.

Bohr

Mar 3, 1913

-Applied quantum theory to Rutherford's atomic structure
-discovered that electrons travel in seperate orbits
-his atomic model shows atoms as small, positvely charged nucleus surrounded by orbiting electrons

Heisnberg and Schrodinger

Mar 3, 1920

-Discovered that no experiment can measure the postion and momentum of an atom
Heisnberg uncertainly principal cloud surrounding the necleus

Aristotle

Mar 2, 2022

With his thory he did not believe in atoms. He believe what he saw on earth with the 4 elements Fire, Air, Water, Earth. He made his discovery through observation.