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400
Democritus Model
Democritus was an ancient Philosopher who first used the term atom. He described the atom using his opinions around the year 400 BC. He described their structure as an eye hanging from a hook form. According to Democritus' recorded opinions he believed that water was an atom as well as salt and that their atom structures were based on their roughness or smoothness. No records have been found of mathematical calculations or conducted experiments -
Period: 400 to
History of the Atomic Theory
The HIstory of the Atomic Theory -
John Dalton's Theory
After centuries John Dalton is the first scientist to restate the theory of the existence of atoms and how atoms are made of elements. He started out by thinking deeper about the origin of evaporation and how it was possible and later restated Democritus' atomic theory. He continued the study by eexperimenting with different gases to observe their properties. -
Michael Faraday's Contribution
Faraday was a scientist who demonstrated the relationship between the magnetic field and electric field of an atom. He proposed that around the nucleus is a magnetic field which corresponds with the electric field where electrons rapidly orbit in. -
Dmitiri Mendeleev's Contribution
Mendeleev was a scientist famous for his contributions to the periodic table. Dueing his time only 63 elements were discovered. He recorded atomic masses that were incorrect. He believed the periodic table should be ordered in ascending order of atomic mass because he found that elements with similar atomic masses had similar chemical or physical properties. This resulted in the breaking of scientific laws rendering the periodic table unreliable or invalid. -
Marie Curie's Contribution
Along with Henry Becquerel. Curie studied particle emitting from atoms. This lead Curie to later state that therefore the previous assumption that atoms are not interchangeable was incorrect. She went on to explain that atoms can be rearranged. particle emitting was mistaken for radiation rays at the time and therefore lead to the series of events to the statement that atoms can be rearranged. -
J.J. Thomson's Contribution
Thomson was known for his identification of electrons in atoms. By using cathode rays he showed how atoms had negatively charged particles then called corpuscles. He claimed that atomic models should not only contain electrons but also an equal amount of positive charge to keep the atom neutral. -
Philipp Lenard's Contribution
Lenard was the identifier of the Dynamid Model a model that simply contains a positively chard and negatively charged particle bound together in a diamond shape. Lenard made extensive observations regarding electron behavior. He stated that the ability of a material to attract electrons is by its mass and not it's chemical properties. He believed that all atoms were composed of the same pieces and what differentiates the amounts of the "pieces" -
Robert Millikan's Contribution
He created the oil drop experiment. It was a method to determine, detect and measure the effect of one subatomic particle. -
Ernest Rutherford's Contribution
Rutherford's theory is that atoms' mass is mostly from it's positively charged nucleus which is surrounded by negatively charged electrons as well as the atom being mostly composed of empty space. This was a result of a gold foil experiment he conducted with his students in which radioactive particles were shot at a piece of gold foil. The experiment resulted in deflection of the particles and the foil still in one piece -
Henry Moseley's Contribution
Henry Moseley was a scientist who worked under Ernest Rutherford. His contribution to the atomic theory was by creating a more accurate arrangement of elements in the periodic table of the elements. He found that the X-Ray emissions of the elements coincided with the elements by atomic number. When isotopes were discovered, Medeleev's theory of atomic mass ordering elements was dismissed and replaced with Moseley's. -
Niels Bohr's Contribution
Bohr was the demenstrator of the bohr model. He followed Ernest Rutherford's experiments and studies to create his version of the atomic model. He obtained the Rydberg Formula to create an imporved model of the atom. Bohr's Model is still used today. -
James Chadwick's Contribution
Chadwick was best known for his discovery of the neutron. He stated that the nucleus had another component called the neutron, a neutral charged particle. According to a source he spent almost a decade trying to identify the neutron. He performed a radiation test to emit radiation from atoms and later detect through a geiger counter, a device which measures the amount of radiation. Chadwick knew it was neutral due to physical reactions that did not occur like not being affected by a magnetic fie -
Werner Heisenberg's Contribution
Heisenberg was best known for his work in uantum physics as well as his winning of a nobel prize. He is also known to have developed the uncertainty principle in which it is stated hat electrons do not travel in neat orbits.
