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Period: 300 to
Atomic Theory
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460
Democritus
Democritus was born in around 475 BCE and it is beleived he died past his 100th birthday. He grew up in Abdera, Greece but worked in Egypt, Ethiopia, Persia, and India. He expanded on his instructor Leucippus' knowledge. He beleived you could not divide something infinitely. He argued for the fact that nature, void space, and motion had existed for eternity. He thought that the atoms to were "impenetrable" and that they have a density proportionate to their volume. -
Antoine Lavoisier
He was a French chemist who was born in 1743 and died by beheading in 1794. He proposed the Law of Conversation of Mass. He also named oxygen and studied the burning proccess. He had a significant impact on modern chemistry. -
John Dalton
John Dalton was born September 6, 1766, in Eaglesfield, England. It was in the year 1803 that Dalton discovered atoms while working with gases. Although earlier people had had theories about atoms before him it was Dalton's theory that was the first accepted theory. This discovery paved the way for more specific discoveries such as the discoveries of protons, nuetrons, and electrons. In order to honor his work, scientists referred one atomic mass unit as 'Dalton' for a while after his death. -
Cathode Ray Tube
The Cathode Ray Tube was what made television possible. The first was invented in 1855 in Germany by Heinrich Geissler called the Geissler Tube. In 1879 the Braun Tube was the forerunner of todays modern television tubes. -
J.J. Thomson
Thomson was born in Manchester, England in 1856. He went to Cambridge University and eveltually to the Cavendish Laboratory at the university. He contibuted heavily to science with his discoveries of isotopes and electrons, which he called corpsucles. One of Thomson's students continued his research that lead to the invention of the mass spectography. -
Dmitri Medeleev
He was born Febuary 8, 1834 and died Febuary 2, 1907. He arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights" and this came to be known as Periodic Law. -
Henry Moseley
November 23 was his birth day and he died on August 10, 1915. He arranged the periodic table by atomic number. His research lasted only four months and happened while Rutherford and Bohr were developing their theories. -
Plum Pudding Atomic Model
This model of an atom was created by J.J. Thomson. It shows electrons floating in a glob of positive substance. Though incorrect to was a stepping stone to the later, and more accurate Bohr Model. -
Robert Millikan
He was born on March 22, 1868 and died in 1953. He made many discoveries including dicovering the charge of an electron, extending the ultraviolet spectrum, and the law of motion. -
Gold Foil Expirement
Due to this expirement we now know that the atom is mostly empty space and has a central positive nucleus. This experiment involved firing radioactive particles through thin metal foils and detecting them using screens coated with zinc sulfide. The results were published in 1911. The expirement was performed by Ernest Rutherford. -
Ernest Rutherford
He was born August 30, 1871 and died October 19, 1937He found out that the nucleus was positivily charged and assumed the electrons were on the outside of the nucleus. He also did the gold foil expirement. -
Bohr Planetary Model
The Bohr Model is a model of the atom complete with electrons, neutrons, and protons. It has become the symbol of the atom in modern times. It was introduced by Neils Bohr in 1913. -
Erwin Schrodinger
He was born on August 12, 1887 and died on January 4th, 1961. He expanded on Bohrs model to make the quantum mechanical model of the atom. He was also the discoverer of the neutron. -
James Chadwick
James Chadwick was born in Cheshire, England in 1891. He proved the existence of neutrons in 1932. Chadwick won the 1935 Nobel Prize in Physics. Due to his work the atomic bomb was made possible. -
Law of Conservation of Mass
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Electron Cloud Model
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Niels Bohr
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Dalton's Atomic Theory
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Rutherford Model
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Quantum Mechanical Model
