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460
Democritus (460 - 370 BC)
Democritus was an ancient greek philosipher who created the atomic theory. He claimed that everything is made up of atoms, they are indestructible, they are always in motion, and that there are an infinite amount of atoms that differ in shapes and sizes. -
Period: 460 to
Atomic Theory
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Antoine Lavoisier
Antoine Lavoisier is considered to be the "Father of Modern Chemistry." He helped construct the metric system, wrote the first exstensive list of elements, predicted the existence of silicon, and was the fist to claim that sulfur was an element, and not a compound. He is most known for discovering the role of oxygen in combustion. -
John Dalton (1776 - 1844)
John Dalton is mostly known fr his work in developing the modern atomic theory, and his research into colour blindness. He expanded on Democritus' theory and created a neww one.
1. Elements are made of atoms
2. Atoms of the same element are identical in size and mass, while atoms of different elements differ in these properties
3. Atoms cannot be made or destroyed
4. Atoms of different elements can combine to form compounds
5. In chemical reactions, atoms are combined, seperated or rearranged -
Dmitri Mendeleev (1834 - 1907)
Dmitri Mendeleev was a Russian chemist and inventor. He was the person to create the first Periodic Table; arranging the 63 known elements based on atomic mass when he published Principles Of Chemistry in 1869. -
J.J. Thomson (1856 - 1940)
Joseph John Tomson is credited with the discovery of the electron. He showed that cathode rays were composed of an unkown negatively charged particle, leading to the discovery. The experimentation of cathode rays is credited to J.J. Thomson, as he was able to deflect cathode rays in a series of experiments. -
Robert Milikan (1868 - 1953)
Robert Andrews Milikan was an American physicist who won the Nobel Prize in 1923 for his measurement off the electronic charge and his work on the photoelectric effect. -
Ernest Rutherford (1871 - 1937)
Ernest Rutherford is considered the "Father of Nucler Physics." He was the first to theorize that atoms have their charge concentrated in a very small nucleus. He created the Rutherford Model to prove this and climed that J.J. Thomsons "plum pudding" model was incorrect. -
Niels Bohr (1885 - 1962)
Niels Bohr was a Danish physicist who developed the Bohr model of the atom. Commonly known as the "Bohr - Rutherford diagram", he expanded on Rutherfords model by saying the atom has a small positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus. -
Erwin Schrodinger (1887 - 1961)
Erwin Schrodinger was an Austrian physicist and was famous for formulating the 1926 wave - equation that accurately gave the energy levels of atoms. -
Henry Moseley (1887 - 1915)
Henry Moseley was a British chemist who studied under Ernest Rutherford and developed the application of X-ray spectra to study atomic structure. His discoveries resulted in the elements being placed more accurately on the periodic table. -
James Chadwick (1891 - 1974)
James Chadwick was an English physicist who won the Nobel prize in 1935, for his discovery of the neutron in 1932.
