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400 BCE
Democritus
-Lived from c.460-c.370 BC
-Born in Abdera, Greece and died in Greece.
-The universe and all matter is made of atoms which are indivisible physically but not geometrically.
-He broke a seashell over and over until it was a fine powder that he could not break up anymore. This idea led to the discovery of the atom.
-Democritus stated that atoms separated at the seams once they attached together.
-Democritus used his wealth to travel and learn from other scholars
-first evidence based theory -
John Dalton
-Known for first evidence based atomic theory
-1) He said that all matter is made of atoms. Atoms are indivisible and are also indestructible. 2) All atoms of an element are identical in mass and properties. 3.) Compounds are formed by a combination of two or more different atoms.
-Born September 6, 1766, in Eaglesfield, United Kingdom
-Died July 27, 1844, in Manchester, United Kingdom
-English chemist and meteorologist
-Discovered in 1803
-his model is referred to as the billiard ball model -
J.J. Thomson
-Born Dec. 18, 1856
-Died Aug. 30, 1940
-Born in Manchester, England
-Thomson was an English physicist and Nobel Laureate in Physics
-Known for the discovery of Electrons through the Plum Pudding Model.
-J.J. Thomson discovered the electron by experimenting with a cathode ray. He demonstrated that cathode rays were negatively charged. So, Thomson understood that the accepted model of an atom did not stand for negatively or positively charged particles. -
Robert Millikan
-born on March 22, 1869, died on December 19, 1953
-born in Morrison, Illinois
-(Oil Drop)his major success was the determination of the change carried by an electron by using the falling-drop method, he proved that this constant was the same for all electrons(1910)
- he made the first direct photoelectric determination of Planck’s constant h (1912)
-he became a professor and simplified teaching methods for physics
-he played a major part in developing anti-submarine and meteorological devices -
Ernest Rutherford
-Born August 30, 1871, in Brightwater, New Zealand
-Died October 19, 1973, in Cambridge, United Kingdom
- Discovered atoms have a small charged nucleus surrounded by empty space, and circled by tiny electrons.
-performed the gold foil experiment; shot particles at sheet of gold foil:some deflected, most passed
- a physicist who became known as the father of nuclear physics
-an atom's mass is mostly in the nucleus/electrons are in a fixed orbit
-Created the Rutherford model to describe an atom. -
Neils Bohr
-lived from October 7, 1885, to November 18, 1962
-He lived in Copenhagen, Denmark
-He proposed the theory of the hydrogen atom stating that energy is only transferred in certain defined quantities; electrons move around a nucleus in designated orbits.
-explains why atoms release a light quantum in fixed wavelengths.
-He came up with the theory because all atoms emit or absorb radiation when they jump from place to place (indicating the light).
-The Bohr Model
-great student, not writer -
Erwin Schrodinger
-Born: August 12, 1887, Erdberg, Vienna, Austria
-Died: January 4, 1961, Vienna, Austria
-Austrian Physicist
- Schrodinger used equations to describe how to find an electron in a certain position.
-his atomic model is the quantum mechanical model of the atom
-Found the wave equation for electron movements -
James Chadwick
-Born October 20, 1891, in Bollington, United Kingdom
-Died July 24, 1974, in Cambridge, United Kingdom
-Awarded a Nobel prize, wrote the final draft of the MAUD report
Awarded Hughes medal of the royal society, Copley medal, Franklin medal, and was knighted in England for his achievements
-British physicist
-known for discovering the neutron
-Said the atom contains in its core a neutron
-His model is the quantum mechanical model
