1900-1915+(VC)

=Robert Millikan =

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-In 1909 Robert Millikan did his oil drop experiment to determine the charge of an electron, which consisted of two charged plates, an x-ray, and oil. Millikan slowly dropped oil through a pinhole and shot each drop with an x-ray giving it a charge. If the charges were negative they would float up to the positive plate. Mostly all of the oil was attracted to the positive plate and the others either floated up near it or fell because they did not have a strong enough charge. With this Millikan determined the electron has a negative charge to it.

__**Robert Millikan's Bio**__ Robert Millikan was born March 22, 1868 in Morrison, Illinois. He entered Oberlin College in Ohio in 1886 and graduated in 1891 where he went on to teach elementary physics. Millikan made many major discoveries in optics, electricity, and molecular physics. His earliest discovery however was made in 1909 when he accurately determined the charge of an electron. During World War I Millikan was the Vice-Chairman of the National Research Council, playing a major part in developing anti-submarine and meteorological devices. Later he was made Director of the Norman Bridge Laboratory of Physics at the California Institute of Technology in 1921 and retired in 1946. He received many prizes for his work including the Nobel Prize in 1923 for physics. Robert Millikan died on the 19th of December, 1953, in San Marino, California.

__**Neils Bohr **__ __http://www.scientific-web.com/en/Physics/Biographies/images/NielsBohr1.jpg__

-Bohr’s discovery was based on Rutherford’s idea that atoms where made up of mostly empty space with positively charged electrons orbiting a small, dense positively charged nucleus. Bohr’s knew that if this was true then the negatively charged electrons would be sucked down onto the positively charged nucleus. Bohr discovered that electrons exist at set energy levels. He also discovered that atoms contain a nucleus at the center that is surrounded with electron shells which have electrons that orbit the nucleus at different energy levels. Electrons with the most energy would be on the outermost shell, and electrons with the least energy are contained on the innermost shells. Electrons cannot exist anywhere in between the shells like previously believed by scientists.

__**Neils Bohr's Bio**__ Niels Bohr was born in Copenhagen, Denmark on October 7, 1885. His father, Christian Bohr, was the Professor of Physiology at Copenhagen University and played a very important role in Niels Bohr’s interest in physics. In 1903 he went to the University of Copenhagen and got his Master's degree in Physics in 1909 and his Doctor's degree in 1911. That same year Bohr went to Cambridge to work under the guidance of Sir JJ Thompson and in the spring of 1912 he went to work in Ernest Rutherford’s lab in Manchester where he passed on to a study of the structure of atoms on the basis of Rutherford's discovery of the atomic nucleus. By using quantum theories Bohr was able to draw up and present a representation of the atomic structure. Recognition of the structure of the atom won Niels Bohr a Nobel Prize in physics for his work. During World War II the Nazi’s occupied Denmark, during this time Bohr escaped to Sweden and then on to England and the United States. Then Niels Bohr, after a long life of accomplishments, died in 1962 at the age of 77.


 * Marie Curie **



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-Marie Curie’s study of radium and the chemical reactions taking place within it changed the minds of the scientific world and the belief that atoms were invariable. “Furthermore, radioactivity is a property of the atom of radium; if, then, it is due to a transformation, this transformation must take place in the atom itself. Consequently, from this point of view, the atom of radium would be in a process of evolution, and we should be forced to abandon the theory of the invariability of atoms, which is the foundation of modern chemistry [M. Curie 1904].” __Curie's Bio__ ** Marie Curie was born in Warsaw, Poland on November 7, 1867. In 1891 during the occupation of Poland by Russia, Curie went to Paris to continue her studies at the Sorbonne where she obtained Licenciateships in Physics and the Mathematical Sciences. While in Paris she met her husband Pierre Curie who together they worked on their isolation of polonium and radium. After her husband’s death Marie Curie took over his position as Professor of General Physics in the Faculty of Sciences and doing so became the first woman ever to hold this position. Marie and her husband received half of the Nobel Prize for Physics along with Becquerel in 1903 for their studies of spontaneous radiation. Then in 1911 she received a second Nobel Prize but this time for chemistry. Curie died in Savoy, France, after a short illness, on July 4, 1934.
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 * Ernest Rutherford**

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-Rutherford put a thin gold foil in the center of a detecting screen and then started to shoot alpha rays through it. Instead of going straight through the foil the ray skimmed off the nucleus and bent different ways, but what really surprised him was when the alpha rays actually bounced back at him. He determined that there had to be something inside the atom that was making it bounce back. For this discovery of the nucleus and the proton Rutherford is known as the father of nuclear physics.

__**Rutherford's Bio**__ Ernest Rutherford was born on August 30, 1871, in Nelson, New Zealand. 1894, he was awarded an 1851 Exhibition Science Scholarship, enabling him to go to Trinity College, Cambridge, as a research student at the Cavendish Laboratory under [|J.J. Thomson]. In 1911 Rutherford conducted his gold foil experiment and discovered the nucleus. Rutherford was knighted in 1914. e died in Cambridge on October 19, 1937. His ashes were buried in the nave of Westminster Abbey, just west of Sir Isaac Newton's tomb and by that of Lord Kelvin.