History of Atomic Theory Project

Democritus

420

[www.egs.edu/library/democritus/biography/](www.egs.edu/library/democritus/biography/)Democritus Was born in Abdera, Greece in 460-370BC. He was an ancient Greek philosopher. He is known for his influence on modern science more than any other pre-socratic philosopher. He was known as the 'Laughing Philosopher'. He was the first person to create an atomic theory. His theory said that all matter is made of atoms.

John Dalton

Jan 17, 1808

http://www.biography.com/people/john-dalton-9265201He was Born September 6, 1766 and died July 26, 1844. In the 1800s, he was the first scientist to explain the behavior of atoms in terms of measurement of weight. He did experiments to measure the weight of the atoms. All items are identical in mass, shape and size.

J.J Thomson

Jan 26, 1897

http://www.nobelprize.org/nobel_prizes/physics/laureates/1906/thomson-bio.html
He was born December 18, 1856 and died August 30, 1940. He discovered subatomic particles that have postive and negative charges. Thomson eperimented with the cathode Ray. His diagram represented a chocolate chip cookie.

Ernest Rutherford

Feb 2, 1899

He was born August 30, 1871 and died October 19, 1937. In 1907, Rutherford, Hans Geiger and Ernest Marsden carried out the Geiger-Marsden experiment, an attempt to examine the structure of the atom. The surprising results of this experiment demonstrated the existence of the atomic nucleus and became an integral part of the Rutherford model of the atom.

Niels Henrik David Bohr

Feb 22, 1913

http://www.nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-facts.htmlHe was born in Copenhagen on October 7, 1885 and died in Copenhagen on November 18, 1962. In 1913, Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted. Bohr's theory could explain why atoms emitted light in fixed wavelengths.

Francis Aston

Apr 7, 1919

http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1922/aston-bio.htmlHe was born in September 1877 and died November 20 1945. Returning to the Cavendish Laboratory in 1919, he again attacked the problem of the separation of the isotopes of neon. He quickly achieved success in this by his invention of the mass spectrograph, an apparatus in which the ingenious use of electromagnetic focusing enabled him to utilize the very slight differences in mass of the two isotopes to effect their separation.

Max Planc

Apr 16, 1922

http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch6/bohr.phpHe was born Apirl 23, 1858 and died on October 4 1947. Max Planck presented a theoretical explanation of the spectrum of radiation emitted by an object that glows when heated. He argued that the walls of a glowing solid could be imagined to contain a series of resonators that oscillated at different frequencies. These resonators gain energy in the form of heat from the walls of the object and lose energy in the form of electromagnetic radiation.

Werner Heisenberg

May 8, 1925

http://www.nobelprize.org/nobel_prizes/physics/laureates/1932/heisenberg-bio.htmlHe was born on December 5 1901 and died on Febuary 1, 1976.
Heisenberg's name will always be associated with his theory of quantum mechanics, published in 1925, when he was only 23 years old. For this theory and the applications of it which resulted especially in the discovery of allotropic forms of hydrogen, Heisenberg was awarded the Nobel Prize for Physics for 1932.

Louis de Broglie

May 27, 1929

http://www.nobelprize.org/nobel_prizes/physics/laureates/1929/broglie-bio.htmlHe was born on August 15 1892 and died on March 19 1987. Discovered the wave nature of the electrons.

James Chadwick

Mar 30, 1932

http://www.nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.htmlHe was born on October 20, 1891 and died July 24 1974. In 1932, Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence of neutrons - elementary particles devoid of any electrical charge. In contrast with the helium nuclei (alpha rays) which are charged, and therefore repelled by the considerable electrical forces present in the nuclei of heavy atoms, this new tool in atomic disintegration need not overcome any electric barrier and is capable of penetratin

Erwin schrodinger

Apr 30, 1933

http://www.nobelprize.org/nobel_prizes/physics/laureates/1933/schrodinger-bio.htmlHe was born on August 12, 1887 and died on Januarry 4 1961. It came as a result of his dissatisfaction with the quantum condition in Bohr's orbit theory and his belief that atomic spectra should really be determined by some kind of eigenvalue problem. For this work he shared with Dirac the Nobel Prize for 1933.

Paul Dirac

May 1, 1933

http://www.nobelprize.org/nobel_prizes/physics/laureates/1933/dirac-bio.htmlhttp://www.nobelprize.org/nobel_prizes/physics/laureates/1933/dirac-bio.htmlHe was born on August 8 1902 and died on October 20 1984. The importance of Dirac's work lies essentially in his famous wave equation, which introduced special relativity into Schrödinger's equation. Taking into account the fact that, mathematically speaking, relativity theory and quantum theory are not only distinct from each other, but also oppose each other, Dirac's work could be considered a fruitful reconciliation between the two theories.