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465 BCE
Democritus
Democritus adopted the atomic theory. His atomic theory stated that atoms cannot be destroyed, it can differ in size, shape and temperature, it's always moving, and are invisible. Also there are an infinite number of atoms. Democritus also created the 1st atomic model -
384 BCE
Aristotle
Aristotle did not believe in the atomic theory. Instead he believed all materials on earth were made up of earth, fire, water, and air. Even though Aristotle's theory is false he had other accomplishments. Aristotle developed the scientific method and had many accomplishments in philosophy. -
Period: 384 BCE to
History of the Atomic Theory
The history of the atom. -
Antoine Lavoisier
Lavoisier (father of modern chemistry) based his experiment on turning HgO into Hg+O he came up with the law of conservation. The law states matter cannot be destroyed or made. This began the conversation on what an atom was exactly. Lavoisier was a great scientist and was known for this experimentation skills. -
Joseph Proust
Proust published his law of definite proportions. The law states that a compound is composed of exact proportions of elements by mass regardless of how the compound was created. To prove his law Proust studied copper carbonate, 2 tin oxides, and 2 iron sulfides. His findings set up Dalton to create the law of multiple proportions. -
John Dalton
Dalton revived the Atomic theory based on his research into the nature of gases. His atomic theory states:
1) All matter is made of atoms. Atoms are indivisible and indestructible
2)All atoms of a given element are identical in mass and properties
3)Compounds are formed by a combination of 2 or more different kinds of atoms
4)A chemical reaction is a rearrangement of atoms
In addition with his theory, Dalton also studied meteorology and weather conditions. -
J.J. Thomson
Thomson discovered the electron by experimenting with a crookes. He demonstrated cathocle rays are negatively charged and particles in neon gas are positively charged particles. Thomson then created a model of the atom that had positive and negative charges. Thomson compared the structure to plum pudding. The negative charges representing the "raisins" and the "dough" is where the positive charges would be located. -
Robert Millikan
By using the "falling drop method" Millikan was able to accurately determine the charge carried by an electron. In addition he proved that this quantity was a constant for all electrons which demonstrated the atomic structure of electricity. In addition to his accomplishments he verified Einsteins photoelectric equation with his experiments. -
Ernest Rutherford
By using his gold foil experiment, Rutherford proved that Thomson's model is incorrect. Rutherford discovered that the alpha particles would sometimes deflect off the foil. Rutherford concluded that atoms is mostly empty space and it has a tiny, heavy, positive charged nucleus. Rutherford was awarded the 1908 Nobel prize in chemistry. -
Niels Bohr
Bohr created a theory that stated that energy is transferred only in certain well defined quantities. This theory explained why atoms emitted light in fixed wavelengths. Because of his discoveries he received a Nobel prize in 1922. -
Louis de Brogile
De Brogile discovered that electrons can act like waves. Waves produced by electrons contained in the orbit around the nucleus, set up a standing wave of a certain energy, frequency, and wave length. Based on these ideas de Brogile developed the wave mechanics theory. He received the Nobel prize in physics in 1929. -
Werner Heisenberg
Heisenberg calculated the behavior of electrons, and subatomic particles that also make up an atom. Heisenberg contributed by adding quantum mechanics. Heisenberg was appointed the professor of Physics at the university of Munich. -
Erwin Schrodinger
Schrodinger used mathematical equations to describe the likelihood of finding an electron in a certain position. A.K.A. the quantum mechanical model of an atom. This would predict the odds of the location of the atom. The model introduced the concept of sub-energy levels. His findings is celebrated as the most important achievements in 20th century physics.
