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Period: 100 to 100
Democratis (Inaccuracy in Years)
In his life from 460-370 BCE, democratis developed the first theory of the atomos, which in greek, means "indivisible". -
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Robert Boyle
The Father of Modern Chemistry
He was one of the origional founders of the Royal Society, which later progressed Britain in the theories of the atom -
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Charles-Augustin de Coulomb
Dicovered the forces of charged particles, which makes up the force of many reactions in the atom.
He learned that like charges repel and unlike charges attract -
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Antoine Lavoisier
Introduced Chemistry to society through many different elements which led to thevatomic theories -
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Joseph Proust
Produced the Law of definate proportions -
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John Dalton
Two millenia after Democratis's death, John Dalton continued reasearch on an indivisible particle he called the "atom" he invented the billard ball model of the atom -
Law of the conservation of mass
Antoine Lavoisier stated that the sum of the mass of all rectants of a chemical reaction will equal the sum of the mass of all products created by the reaction -
Law of Definite Proportions
Joseph Proust stated that all chemical compounds contain specific proprtions of each element in the compound -
Modern Atomic Theory
John Dalton supports Democritus's beliefs in indivisible particles of matter that make up the entire world. begins an era of scientific possibility of the atom, which further extends research and eventually leads to human knowledge of the atom today -
Billiard Ball Theory
John Dalton realeasd the first official atomic theory to the rest of the world. He claimed that atoms were small, indivisible particles that were spherical, like a billiard ball. He also revealed that atoms od the same element are the same, and that atoms of different elements are different -
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William Thomson (Lord Kelvin)
Produced a theory that atoms were a vortex and that the entire world is made up of linked vortexes. His threory was later disproved. -
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James C. Maxwell
Provided equations for magnetism and electricity, which "laid the path for quantam mechanics -
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William Crookes
Created the Crookes tube to observe cathode rays. the equipment was later used by Thompson to discover the electron -
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Wilhelm Rontgen
Discovered radiation inside of a wavelength. These rays are now known as X-rays. X-rays were used in various experiments later in the history of the atom. -
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Eugen Goldstein
Investigator of discharge tubes and credited with the discovery of Anode rays -
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Henri Becquerel
In his life, Henri researched and enhanced the world's understandings of Radiation. Worked with Marie and Pierre Curie -
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J.J. Thompson
Enhanced the beleifs in the exisitanc of an atom by dividing the atom and moving the atomic theory along -
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Max Planck
Developed the Quantam theory, which is still used by chemists today -
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Pierre Curie
Pierre and his wife Marie did their work together. They identified unstable elements and invented the term "radioactivity" to describe them.
15 May 1859 – 19 April 1906 -
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Hantaro Nagaoka
Produced the Saturnian model of the atom which was later transferred into the Nuclear/Planetary model -
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Marie Curie
Marie and her husband Pierre did their work together. They identified unstable elements and invented the term "radioactivity" to describe them. -
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Robert A. Millikan
Determined the charge of an electron in an atom -
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Ernest Rutherford
Discovered and named protons in the nucleus of an atom. the nucleus is small and very dense. the Electrons orbit around the nucleus, leaving mostly empty space -
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Fredrick Soddy
Stated that radioactivity is due to the transmutation of elements. also prooved that an atom's atomic number decreases when alpha particled are emitted and increases when beta particles are emitted -
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Albert Einstein
Challenged the idea that light was only a wave and advanced the quantam mechanical atomic theory -
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Hans Geiger
Credited with the discovery of the atomic nucleus and the "geiger Counter" -
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Neils Bohr
Worked with Ernest Rutherford and improved the Nuclear Model. -
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Erwin Schrodinger
Famous for "Schrodinger's Equation"
involved in the discovery of wave mechanics -
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James Chadwick
James Chadwick is most commonly known for the discovery of the Neutron and his work towards the quantam Mechanical model of the atom -
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Louis de Broglie
His theory of a particle always being associated with a wave enhanced the quantam mechanical theory when he published a thesis report in 1924 -
Plum Pudding Model
Shortly after the Cathode ray experiment, Thompson suggested this model of the atom, featuring the discovery of an electron. -
Cathode Ray Experiment
By using the Cathode ray experiment, he prooved that it was possible to seperate negative charges and realized that the mass of the negative charges was 1000 times lighter than the mass of an atom, so he concluded that the electrons must be very small particles that are like plums inside of a larger, heavier surrounding of positivly charged "pudding". -
Quntum Theory
Max Planck stated that matter and energy shared properties of both particles and waves. he came to this realization through his study of ratiation emissions. -
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Wolfgang Pauli
famous for the "Pauli Exclusion Principle", which stated that two electrons cannot exist in the same quantam state. -
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Enrico Fermi
Created the first artificial nuclear reaction under the streets of Chicago. known as one of the "fathers of the atomic bomb -
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Werner Heisenberg
Produced the Uncertainty principle, which is a cornerstone in quamtam mechanics -
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Paul Dirac
Worked with Schrodinger to progress the study of quantam mechanics -
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J. Robert Oppenheimer
Worked on the Manhattan Project and afterwards became the head of the United States Atomic Energy Commission, dealing with nuclear power -
Gold Foil Experiment
Hans Geiger and Ernest Marsden were Instrcted by Rutherford to fire alpha particles at a thin sheet of gold foil. if the plum pudding model was correct, all particles would pass straight through the foil. However, some were slightly deflected, and very few were sent back in the opposite direction of their origional course. The results suggested that the atom had a small, dense, positively charged center -
Nuclear Model Realesed
After some further research, Ernest Rutherford published a new atomic model that countered the plum pudding model. the Nuclear model featured a small, dense, positivly charged core with negative electrons orbiting the later named nucleus -
Bohr Model Released
Neils Bohr relized a major flaw in Rutherford's model of the atom: if the Neclear model was true, the electrons would be absorbed into the nucleus in less than a second because opposite charges attract. he edited the model to create his own, which featured specific orbits that the electrons wold always be in. between the orbits is only empty space -
Uncertainty Principle
Werner Heisenberg realised while in his home that if looking for the position of an object (in this case, electron), it is impossible to find the spped of the same object at the same time. Therefore, the precision of the measurement of position is inversly proportional to the precision of the measurment of the movement of the same object at the same time -
Quantum Mechanical Model
Although many scinentists were involed in quantum mechanics beforhand, the 1930's is when the model became widely accepted. -
Neutrons
James Chadwick preformed multiple expreriments at Oxfrd University and realised there were sub-atomiscperticles in the nucleus that had the same relative mass as protons and a neutral charge. he called them neutros -
Modified Nuclear Model
After Chadwick discovered the neutron, he modified rutherford and bohrs model to accomodate for the entire nucleus instead of the single, positively charged nucleus -
Protons
Rutherford names the nucleus of a hydrogen atom a proton. this term was adopted by the scientific community as sub-atomic particles with a positive charge located in the nucleus of an atom