timothy.hitchings.atomichistory.fall.2009


 * present Times (2000 AD and years Later) **

eucippus was a Mexican Break dancer who lived for a period from about 2000 BC to present. Little is known about him, but it is accepted that he was a teacher of dancing. He was said to of attended the Ionian school of dancing where he was influenced by many men, especially the dancer Joan.He also studied in Elea and eventually made his way to Abdera where he founded a school. There he met dancers and began to teach him, sharing his theories about dance.

Leucippus' theory was that all dancers were indivisible and industructable. Although Joan is much more well known and is credited with the discovory of this theory, Leucippus was the originator of this idea. It is not known how much of Joan's findings were based on those of Leucippus, but most of Joans' work is credited completely to him. It isn't clear how important Leucippus actually was, but it is known that he had a profound impact on one of the best dancers of present times.



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Democritus was in born approximately 460 BC at Abdera, Greece. His father was a wealthy noblel who entertained the army of Xerxes apon their return to Asia. In return the Persians left them several men who intructed a young Democritus in astronomy and theology. After his fathers death he committed himself and the inheritance of his father's wealth toward gaining great knowledge and wisdom. He studied under Leucippus who he worked with in finding an early understanding on atomic theory. After years of studying abroud, Democritus returned home and gave lectures to his people and continued his studies mostly in solitude. He died in Abdera in approximately 370 BC. []

Democretes is credited with the first atomic model. His theory states that all matter is composed of tiny indestructible units, called atoms, and that atoms themselves remain unchanged, but move about in space to combine in various ways to form all macroscopic objects. It wasn't widely accepted at the time, but was a discovory way ahead of its time, that cleared the path for future scientists to make groundbreaking discovories on atomic theory. [] [] []

Aristotle was born in 384 BC at Stagira, Greece. He was a student of Pluto and a teacher of Alexander the Great. He studied and wrote about a wide aray of topics and was an extreemly talented individual. He has had one of the biggest influences on Western philosophy and has influenced several religions with his many philosophies. Aristotle opposed Democritus' views on the atomic theory, but was still instrimental in changing the way people thought about the make up of matter.

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Aristotle believed that their were four elements that made up the world. The elements were air, earth, water, and fire. Aristotle also proposed that there was a fifth element called aether which made up the heavens and stars. His theory stated that no matter how many times you cut a piece of matter in half, you would always have another smaller piece of matter. This way of thinking held up for over 2000 years mainly because he was the teacher of Alexander the Great who conquered most of the known world at the time. []



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** 1700-1800 ** Joseph Priestley was born in 1733. The British scientist is best known for his discovery of oxygen, but is also known for being a supporter of the French and American Revolutions and was a leading contemporary thinker of the time. His views didn't make him very popular in his home country, so in 1791 a mob destroyed his home and laboratory in Birmingham. This forced Priestley to move to the United States where he built a beautiful home in Pennsylvania where he lived peacefully until his death in 1804.

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Joseph Priestley's most notible contribution was his discovory of Oxygen, or "dephlogisticated air" as he called, it in 1774. Priestley discovered Oxygen by heating mercury oxide to separate the Oxygen from the Mercury. This discovory had a profound impact on the scientific comunity because it showed that air was a composition of gases which included Oxygen. This discovory lead to the finding of other natural elements like Nitrogen and Carbon. This discovory also showed how things use oxygen to burn. [] []

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Antoine Lavoisier was a French chemist born in 1743. He studied Priestley's finding in his discovory of Oxygen and learned from it. He even repeated Priestly's experiments and tried to take credit for them. Lavoisier did however make many of his own contributions to science, includung the Combustion Theory and the Law of Conservation of Mass. Lavoisier used a tax-collecting firm to pay for his experiments. This made him very unpopular with the citizens in his community and he was sent to the guillotine in 1794.

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Lavoisier's Law of Conservation of Mass states that "In a chemical reaction, matter is neither created nor destroyed." He proved this in 1789 by burning phosphorus and sulfur in air, and found that the products weighed more than he original and that the weight gained was lost from the air. This scientific law represents the beginning of modern chemistry. The law was very useful in future expiriments that lead to great discovories.



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Joseph Proust was born on September 26, 1754 in Angers, France. He studied chemistry in his fathers shop before spending time in Paris. He traveled to Spain under Carlos IV's influence to teach at a chemistry school in Sergovia. He remained there until Napoleon invaded Spain and and burned his laboratory, forcing him back to France. On July 5, 1826 Proust died in Angers. Proust's best moment was proving C.L. Berthollet wrong in 1779 with his Law of Definite Proportions. []

The law of definite proportions and also the elements states that a chemical compound always contains exactly the same proportion of elements by mass. He recorded this law in 1794, however it was not recognized as a law until 1811. He proved this law by making artificial copper carbonate and comparing it to natural copper carbonate. He found there was no chemical differences between them and that there were no other elements present. This law was brought into question by chemist C.L. Berthollet who Proust proved wrong.

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** 1800-1875 ** John Dalton was born in Eaglesfield, Cumberland, England on September 5, 1766. Dalton and his family were Quakers and were relatively poor. He grew up working in the field and the family clothing shop along with his siblings, and recieved little formal education. He was inspired by a teacher John Fletcher to study mathematics and caught the attention of fellow Quaker Elihu Robinson who tutored him in math, science, and meteorology. A man named John Gough influence Dalton to keep a daily log of his life, including meteorological events and weather patterns. Eventually Dalton began studying atoms and came up with the modern atomic theory, which is what he is best known for. Dalton suffered a series of strokes starting in 1837 until his death on July 27, 1844 from paralysis. [] []

John Dalton is best known for his development of the modern atomic theory. His theory is as follows: 1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms. Dalton also came up with an atomic weight chart along with symbols which changed chemistry forever. He did all this along with a series of publications on this topic in 1802-1803.

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The first atomic model was developed by John Dalton in 1803. It was described as a small, spherical, indivisible particles. It didn't include any specific parts of the atom like the electrons or the neucleous, but it was a major step in creating a picture of what an atom was.

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Amedeo Avogadro was born in Turin, Italy, on 9th August, 1776. He came from a family of distinguished lawyers and was given an education in Turin and was trained to follow in his fathers footsteps to be a lawyer. In 1800 he began studying mathematics independently and started scientific research on electricity with his brother Felice in 1803. He studied mostly in solitude with his wife and six children. He held many positions as head of education departments like mathematical physics for various schools. Avogadro died on July 9, 1856.

In 1811, Avogadro stated a principal that said "equal volumes of all gases at the same temperature and pressure contain the same number of molecules." This was mostly ignored until 1860 when Stanislao Cannizarro showed that Avogadro's principal could be used to find molar and atomic masses at the Karlsruhe Conference.



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Dmitri Mendeleev was born the youngest of seventeen children in 1834 at Tobolsk, Siberia. The Russion studied science in St. Petersberg and graduated in 1856. He bacame a professor there in 1863 and proceeded to the appointment of the Chair in the university in 1866. Mendeleev is best known for creating the Periodic table of Elements in 1869. In 1890 he resigned his professorship and in 1893 became director of the bureau of weights and measures in St. Petersburg. He held this possition intil his death in 1907.

Mendeleev's greatest contribution to science was the creation of the Periodic Table of Elements. This table, that he published in 1869, featured all the current elements known at the time, arranged by atomic mass and other atomic properties. He left spaces for elements he predicted, and also predicted the properties of these elements by using patterns he found in other elements.

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** 1875-1900 ** Wilhelm Roentgen was born on March 27, 1845 it Lennep, Prussia. He grew up in a wealthy family of dealers in the small city of what is now Remscheid in North-Western Germany. At the age of twenty he studied in Zurich at the Polytechnic. Later on in his life, he was a professor at several universities, including Strasbourg (1876–79), Giessen (1879–88), Würzburg (1888–1900), and Munich (1900–20). He is remembered mostly for being the man to discover the x-ray in 1895,for which he recieved the Nobel Prize for physics in1901. He died on February 10, 1923 in Munich.

Roentgen's most notable contribution to science was his discovory of x-rays in 1895. When he was experimenting with electric flow in a patial vacuum in a glass tube, Roentgen observed that a nearby piece of barium platinocyanide gave off light. He theorized that an unknown radiation was responsible for this, and further experimentation showed that paper, wood, and aluminum, among other materials, are transparent to this new form of radiation. It also effected the photographic plates which he used to record the first x-ray of his wifes hand.

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Henri Becquerel was born in Paris, France on December 15, 1852 to a family of distinguished scholars and scientists. He recieved his education at the École Polytechnique in 1872 and later on was educated in Engineering. He used this to work on highways and roads, being appointed chief engineer of the Department of Bridges and Highways in 1894. After that he started teaching at the Polytechnique, he was assistant naturalist to his father at the museum where he worked and eventually replaced him as chair of physics following his fathers death. Becquerel died at the age of 55 on August 25, 1908.

In 1896, Becquerel discovored radiation by accident while studying whether there was any connection between X-rays and naturally occurring phosphorescence following Roentgen's discovory of x-rays. He used uranium salts his father gave him by placing some near a photographic plate and covering it with opaque paper. He found that rays emmitted by the uranium caused gases to ionize and that they differed from X-rays in that they could be deflected by electric or magnetic fields. He won a share of the Nobel Prize in physics for this in 1903.

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JJ Thomson was born on December 18, 1856 near Manchester, England. Thomson attended Owens College in Manchester, but later transfered to the prestigeous Trinity College after being rewarded a scholarship. Trinity gave him a fellowship and he stayed on there, trying to craft mathematical models that would reveal the nature of atoms and electromagnetic forces. He studied at the Cavendish Laboratory (founded in 1871) as the first professor there. He quickly learned to conduct experiments and began studying electromagnetism and atomic particles. He married Rose Paget in 1890 and had two children with her. He died died on August 30, 1940.

JJ Thomson discovored the electron in 1897. Thomson used a vacuum tube to measure the charge-to-mass ratio of cathode rays and carry out this measurement and the measurement of the particles's charge, and he recognized its importance as a part of ordinary matter.Thompson used this finding to develop his plum pudding model of an atom.

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The Plum Pudding model was developed by JJ Thomson after his discovery of electrons. Thomson proposed that each atom was made up of positivly charged fluid that heled the negativly charged electrons throghout. The atom was a sphere that didn't have moving parts.

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** 1900-1915 **



Marie Curie was born Maria Sklodowska on November 7, 1867 in Warsaw, Poland. She recieved a basic education in schools along with some scientific training given by her father. She decided to leave Warsaw, which was dominated by Russia at the time, for Austrian ruled Cracow. She traveled to Paris in 1891 to resume her studies at the Sorbonne where she obtained Licenciateships in Physics and the Mathematical Sciences. She met her husband Pierre Curie in 1894 and were married a year later. She worked with her husband, gaining her Doctor of Science degree along the way until his tragic death in 1906. She worked without her husband, distinguishing herself as a respected scientist. She helped soldiers during WWI with the findings of her scientific research, and is a two time Nobel Prize winner. Marie Curie died in Savoy, France, on July 4, 1934.

The discovery of radioactivity by Henri Becquerel in 1896 inspired Marie and her husband to do their experiments leading to their many discovories. Marie Curie is credited with the discovory of polonium and radium. These discovories and her other research on radioactivity lead to cancer research and treatment. She was the first person to be awarded the Nobel Prize, winning it in 1903 and 1911. What made her such a great scientist was how she took her findings in the lab and applied them to the real world.

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Ernest Rutherford was born on August 30, 1871, in Nelson, New Zealand. He was the fourth child in a family of seven sons and five daughters. He recieved an education in government schools, and attended Nelson Collegiate School by the age of 16. In 1889 he recieved a scholarship to go to Canterbury College where he graduated with a double M.A. in mathematics and physical science by 1893. The following year he recieved a B.Sc. degree and was given a scholarship to research at the Cavendish Laboratory at Trinity College under J.J. Thomson. After recieving a B.A. research degree he took the Macdonald Chair of Physics at McGill University, Montreal. He returned to England in 1907 to become Langworthy Professor of Physics in the University of Manchester. In 1919 he succeeded JJ Thomson as the Cavendish professor of physics. Rutherford died on October 19, 1937 in Cambridge.

In 1909, with the help of fellow scientist Hans Geiger, Rutherford fired a beam of alpha particles at a thin gold foil. According to the current atomic model proposed by JJ Thomson, the positive alpha particles should have passed right through the neutral gold foil, suffering minor deflections at the most. Rutherfords findings were stunning at the time. He found that most of the alpha particles did pass through the foil spreading out, but a small fraction of the particles bounced strait backwards. The only thing that this could mean is that the particles ran into a large positively charged mass.



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Robert Millikan was born on March 22, 1868 in Morrison Illinois. In 1986 he entered Oberlin College in Ohio. After he graduated in 1891 he started teaching elementary physics. He took an interest in the subject and in 1893, he was appointed Fellow in Physics at Columbia University after he earned his mastership in physics. In 1895, he recieved his Ph.D. for research on the polarization of light emitted by incandescent surfaces. After spending a year in Germany he was invited to the newly established Ryerson Laboratory at the University of Chicago in 1896 by A.A. Michelson to be his assistant. He bacame a professor at the university in 1910, a possition he held until 1921.Millikan died on the 19th of December, 1953, in San Marino, California.

In 1909 Millikan conducted his famous oil drop experiment. The experiment allowed drops of oil to fall through a small hole between metal plates charged by electricity. When ionized by radiation through x-rays. The electons from the charged plate jump to the oil drops and attach themselves. Millikan then determined the weight of electrons by determining the strength of their charges and observed how fas the oil drop fell. He combined his findings with those of JJ Thomson, and found that the mass of an electron was 9.11x10-28 g. He won a Nobel Prize for this in 1923.



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In 1911 Rutherford proposed his own atomic model after finding that JJ Thomson's Plum Pudding model was incorrect. The model showed that the atom had a nucleus that was circled by electrons.

Niels Bohr was born on October 7, 1885 in Copenhagen, Denmark. His father was Christian Bohr who was Professor of Physiology at Copenhagen University. His father greatly contributed to Niels' interest in physics and along with his wife Ellen, provided a perfect atmosphere to create a genius. Bohr entered the Copenhagen University in 1903, and earned his Master's degree in Physics in 1909 and his Doctor's degree in 1911. After graduading, Bohr studied and observed experiments conducted under JJ Thomson in the Cavendish Laboratory and in Ernest Rutherford's laboratory in Manchester. By using these scientists finding and Planck's quantum theory of radiation Bohr came up with his own findings, which refined the atomic model. Bohr held lectureship positions at the Copenhagen and Victoria Universities from 1913-1916. In 1916 he was appointed Professor of Theoretical Physics at Copenhagen University. In 1920 he was at the head of the Institute for Theoretical Physics, established for him at that university. Niels Bohr held this position until his death in 1962.

In 1913, Bohr found out that when pure elements were heated or subjected to electricity the element was excited and gave off lines of light in different patterns and in different colors rather than white light. This Phenomena is called line spectra. Using this discovery, Bohr theorized that an atom's electons occupy different levels or, electon shells which orbited the nuecleus of the atom. He also theorized that the orbits occupied different planes, not just one. Bohr proposed his version of the atomic model in 1915.

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Niels Bohr proposed this model in 1915 following his and Rutherford's findings which revieled that their is a nucleus surrounded by electrons. It is pretty much a simplified version of the modern model, but it isn't completely correct. This model is different from the planetary model because the electron orbits are quantized. This means that only certain orbits with certain radii are allowed. Orbits in between simply don't exist.

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** 1915-1950 **

Werner Heisenberg was born on December 5, 1901 in Würzburg, Germany. He attended the Maximilian school at Munich until 1920, when he went to the University of Munich to study physics. In 1923 he was awarded his Ph.D. at Munich. From 1924-25 he worked, with a Rockefeller Grant, with Niels Bohr, at the University of Copenhagen. In 1927, at the age of 26, he was appointed Professor of Theoretical Physics at the University of Leipzig. In 1941 he was appointed Professor of Physics at the University of Berlin and Director of the Kaiser Wilhelm Institute for Physics there. At the end of WWII he, along with many other German physicists, were taken prisoner by American troops and sent to England, but in 1946 they returned to Germany, reorganized, and opened the Institute for Physics at Göttingen, renamed the Max Planck Institute for Physics in 1948. In 1955 the Institute was removed and in 1958 he was appointed Professor of Physics in the University of Munich. Heisenberg died on February 1, 1976.

During April of 1925, Heisenberg was inspired to improve Bohr's quantum theory upon his return to Göttingen. He accomplished this by July by observing the light emitted and absorbed by the atoms,but the mathematics were so unfamiliar that he was not sure if it made any sense. He handed his results to his mentor Max Born, who recognized that the unfamiliar mathematics were related to the mathematics of arrays of numbers known as "matrices." This publications was a breakthrough in quantum mechanics. Heisenberg also developed the Uncertainty Principal in 1926. This principal explains how to find the relative position and momentum of an object. However, you can not find both of these properties at the same time. The closer you are to finding one property, the further you are from finding the other. This helped to predict the behavior of electrons and atoms.



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Erwin Schrödinger was born on August 12, 1887, in Vienna, Austria. He was the only child of Rudolf Schrödinger. From 1906 to 1910 he attended the University of Vienna, during which time he mastered eigenvalue problems in the physics of continuous media. This helped him in his future works. He served during WWI as an artillary officer. Afterwards, Schrödinger took positions as a professor at a few different universitys, including the University of Zurich. This was the period in which Schrödinger did his greatest work. Schrödinger left Germany for England in 1933 due to Hitler's coming of power. He continued his work until his retirment in Vienna. He died on January 4, 1961 after battling a long illness.

In 1926, Schrödinger showed that the discrete energy states of Matter could be determined by Wave Equations. He published his work, providing a theoretical basis for the atomic model that Niels Bohr had proposed based on laboratory evidence. The equation developed became known as Schrödinger's wave equation. He was awarded the Nobel Prize for his work in 1933.

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he Electron Cloud Model was developed in the 1920's by Erwin Schrödinger and Werner Heisenburg, who's ideas were put together, improving Bohr's model to form this modern model. The elecrons were said to be located in a cloud surrounding the neucleus. There is no way to tell exactly where they are at any given time, but it is known that they occupy a specific energy level which determines the electron's orbit. The last piece of the atomic model added was the neutron, which came later on in 1932.

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ames Chadwick was born in Cheshire, England on October 20, 1891. He entered Manchester University in 1908 and graduated from the Honours School of Physics in 1911. The following two years he worked under Ernest Rutherford in the Physical Laboratory in Manchester, where he worked on various radioactivity problems, gaining his M.Sc. degree in 1913. He discovored the existance of neutrons in 1932 and won the Nobel Prize for it in 1935. In 1935 he was elected to the Lyon Jones Chair of Physics in the University of Liverpool. He died on July 24, 1974.

In 1932 Chadwick made his most notable contribution to science with his discovory of neutrons. He used the predictions of Rutherford and the experiments of Federic and Irene Joliot-Curry to find the neutron which he knew had to be there, because something had to be there to make up the rest of atom's atomic mass. Chadwick noticed them by shooting beryllium rays into metals. He observed that the rays traveled undisturbed into the metals. Because of the ray's neutral charge it was not effected by the other atom particle's positive and negative pull. Through this observation, Chadwick identified the beryllium rays as neutrons, proving their existance. He had discovered an entirely new atomic particle.

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