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442 BCE
Democritus
An ancient Greek philosopher born around 460 BC in and died around 370 BC in Greece. Everything is composed of atoms and they do not divide geometrically. They are indestructible. They will always be in motion and there are an infinite number of atoms. His model came up in 442 BC. He reasoned that if you took a stone and cut it in half and continued cutting it in half, you would reach a point where it could not be divided anymore. He was known for being a cheerful philosopher. -
John Dalton
September 6, 1766-July 27, 1844, born in Eaglesfield United Kingdom and moved to Manchester UK. Dalton is credited with the first modern atomic theory that proposed that all matter was composed of atoms based on his experiment with atmospheric gases. In 1826, he was awarded the society’s royal metal for his atomic theory -
J.J Thompson
December 18, 1856 - August 30, 1840. Born at Cheetham Hill and went Cambridge Trinity College. Through the cathode ray tube experiment, he discovered electrons by sending cathode rays through a vacuum and calculated the ratio of the electrical charge to the mass of the particles. When he discovered this calculation was the same for every gas, he concluded the particles making up the gas are the same for every gas. He was awarded the Nobel Prize in 1906 and knighted by King Edward VII in 1908. -
Robert Milikan
March 22, 1868- December 19, 1953, born in the United States, more specifically was born in Morrison, IL and moved to California. He discovered the size of the charge on an electron and the value for the electron charge through the oil drop experiment. He was the first to determine with great accuracy that the maximum kinetic energy of the ejected electrons obey the equation Einstein had proposed. He won a noble prize for his study in elementary electronic charge and the photoelectric effect. -
Ernest Ruthorford
August 30, 1871- October 19, 1937 born in New Zealand and moved to England. He dicscovered the nucleus and overturned Thompson’s model in 1911 with his gold foil experiment where he demonstrated that an atom has a heavy positive charged nucleus with negative electrons rotate around kind of like the solar system. Rutherford was a Professor of Physics at the University of Manchester. -
Neil's Bohr
October 7, 1885-November 18, 1962, Copenhagen, Denmark, proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. His theory explained why atoms emitted light in fixed wavelengths being Bohr's model, won a nobel prize for his contribution in investigating the structure of atoms and the radiation produced by them -
Erwin Schrodinger
August 12, 1887- January 4, 1961, lived in Vienna Austria, Schrodinger wave equation- Schrodinger taking Bohr’s theory one step further by describing the likelihood of finding an electron in a certain position. He further explained the nature of electrons in an atom by saying the exact location of an electron cannot be stated, but are in regions called electron clouds, won a noble prize by contributing in quantum physics -
James Chadwick
he was born October 30, 1891- July 24, 1974 in the United Kingdom and he discovered the neutron. In 1930, it was discovered that Beryllium, when it was bombarded by alpha particles, emitted a very energetic stream of radiation.He was the greatest scientist alive during WW1.
