Fall.2008.MMA.Silva.TimelineFall

BY JEREMY SILVA
 * ATOMIC HISTORY TIMELINE

Democritus**




 * Born 460 BC - Died ca 370 BC
 * Country of Origin: Abderba, Thrace

http://www.timelineindex.com/content/view/1228 http://en.wikipedia.org/wiki/Democritus
 * Democritus agreed that everything which is must be eternal, but denied that "the void" can be equated with nothing. This makes him the first thinker on a record to argue the existence of an entirely empty "void". In order to explain the change around us from basic, unchangeable substance he created a theory that argued that there are various basic elements which always existed but can be rearranged into many different forms. Democritus' theory argued that atoms only had several properties, particularly size, shape, and (perhaps) weight; all other properties that we attribute to matter, such as color and taste, are but the result of complex interactions between the atoms in our bodies and the atoms of the matter that we are examining. Certainly Democritus was not the first to propose an atomic theory. His teacher Leucippus had proposed an atomic system, as had Anaxagoras of Clazomenae. In fact traces of an atomic theory go back further than this, perhaps to the Pythagorean notion of the regular solids playing a fundamental role in the makeup of the universe.


 * Aristotle**




 * Born: 384 BC – 322 BC
 * Country of Origin: Chalcidice

http://wiki.answers.com/Q/What_did_Aristotle_find_out_about_the_atom
 * Aristotle did not believe the ancient Greek theory of atoms being different sizes, regular shapes, and being in constant motion. Aristotle didn't think atoms could be in a constant motion in a void. He developed his own theory that all matter consisted of four elements; earth, air, water, and fire. He also added four qualities. These were dryness, hotess, coldness, and moistness. Aristotle's theory also had two forces; conflict and harmony. The conflict force was thought to cause bad things and harmony was thought to cause good things.




 * William Crookes**




 * Born: 17 June 1832 – 4 April 1919
 * Country of Origin: England

http://en.wikipedia.org/wiki/William_Crookes
 * Crookes investigated the properties of cathode rays, showing that they travel in straight lines. He believed that he had discovered a fourth state of matter, which he called //"radiant matter"//. He believed the rays to consist of streams of particles of ordinary molecular magnitude. In 1903, Crookes turned his attention to the newly discovered phenomena of radioactivity.




 * John Dalton**




 * Born: 6 September 1766 – 27 July 1844
 * Country of Origin: England

http://www.answers.com/topic/john-dalton http://www.answers.com/topic/john-dalton
 * Englishman John Dalton was one of the first scientists to decide that all matter is made up of small particles, or atoms. He is also remembered for his weather observations, which he began recording in 1787 using instruments he made himself. His studies led him to develop theories about water vapor and mixed gases, and in 1801 he came up with Dalton's law of partial pressures: that in a mixture of gases, each component exerts the same pressure as it would if it alone made up the whole volume of the mixture. From there Dalton decided that all matter must consist of small particles. He revived the ancient theory of atoms and prepared the first table of atomic weights, and announced his notions publicly in 1803.
 * John Dalton was the youngest of three surviving children of a Quaker handloom weaver. Until he was 11, he attended school, then at the age of 12 became a teacher. For about a year he next worked as a farm helper, but at 15 he returned to teaching, privately for the most part, pursuing it as a career for the remainder of his life.




 * J.J Thomson**




 * Born: 18 December 1856 – 30 August 1940
 * Country of Origin: England

http://nobelprize.org/nobel_prizes/physics/laureates/1906/thomson-bio.htm
 * Joseph John Thomson was born in Cheetham Hill, a suburb of Manchester on December 18, 1856. He enrolled at Owens College, Manchester, in 1870, and in 1876 entered Trinity College, Cambridge as a minor scholar. He became a Fellow of Trinity College in 1880, when he was Second Wrangler and Second Smith's Prizeman, and he remained a member of the College for the rest of his life, becoming Lecturer in 1883 and Master in 1918. He was Cavendish Professor of Experimental Physics at Cambridge, where he succeeded Lord Rayleigh, from 1884 to 1918 and Honorary Professor of Physics, Cambridge and Royal Institution, London.

http://www.aip.org/history/electron/jjhome.htm
 * At the Cavendish Laboratory at Cambridge University, Thomson was experimenting with currents of electricity inside empty glass tubes. He was investigating a long-standing puzzle known as "cathode rays." His experiments prompted him to make a bold proposal: these mysterious rays are streams of particles much smaller than atoms, they are in fact minuscule pieces of atoms. He called these particles "corpuscles," and suggested that they might make up all of the matter in atoms. It was startling to imagine a particle residing //inside// the atom--most people thought that the atom was indivisible, the most fundamental unit of matter.


 * Wilhelm Conrad Roentgen**




 * Born: 27 March 1845 – 10 February 1923
 * Country of Origin: Prussia

http://nobelprize.org/nobel_prizes/physics/laureates/1901/rontgen-bio.html
 * Röntgen's name, however, is chiefly associated with his discovery of the rays that he called X-rays. In 1895 he was studying the phenomena accompanying the passage of an electric current through a gas of extremely low pressure. On the evening of November 8, 1895, he found that, if the discharge tube is enclosed in a sealed, thick black carton to exclude all light, and if he worked in a dark room, a paper plate covered on one side with barium platinocyanide placed in the path of the rays became fluorescent even when it was as far as two metres from the discharge tube. In further experiments, Röntgen showed that the new rays are produced by the impact of cathode rays on a material object. Because their nature was then unknown, he gave them the name X-rays.




 * Henri Becquerel

**


 * Born: 15 December 1852 – 25 August 1908
 * Country of Origin: France

http://en.wikipedia.org/wiki/Henri_Becquerel http://nobelprize.org/nobel_prizes/physics/laureates/1903/becquerel-bio.html
 * In 1896, while investigating phosphorescence in uranium salts, Becquerel accidentally discovered radioactivity. Investigating the work of Wilhelm Conrad Roentgen, Becquerel wrapped a fluorescent substance, potassium uranyl sulfate, in photographic plates and black material in preparation for an experiment requiring bright sunlight. However, prior to actually performing the experiment, Becquerel found that the photographic plates were fully exposed. This discovery led Becquerel to investigate the spontaneous emission of nuclear radiation. In 1903, he shared the Nobel Prize in Physics with Pierre and Marie Curie "in recognition of the extraordinary services he has rendered by his discovery of spontaneous radioactivity"
 * Becquerel's earliest work was concerned with the plane polarization of light, with the phenomenon of phosphorescence and with the absorption of light by crystals (his doctorate thesis). He also worked on the subject of terrestrial magnetism. In 1896, his previous work was overshadowed by his discovery of the phenomenon of natural radioactivity.




 * Marie Curie

**


 * Born: 7 November 1867 – 4 July 1934
 * Country of Origin: Poland

http://nobelprize.org/nobel_prizes/physics/laureates/1903/marie-curie-bio.html
 * Curie's earlier researches were usually often performed under difficult conditions. Her labratory conditions were poor and she had to undertake much teaching to earn a livelihood. The discovery of radioactivity by Henri Becquerel inspired Marie, along with her husband, which later led to the isolation of polonium and radium. Curie developed methods for the seperation of radium from radioactive residues in decent quantities to allow for its characterization and the careful study of its properties.




 * Ernest Rutherford**




 * Born: 30 August 1871 – 19 October 1937
 * Country of Origin: England

http://www.rsc.org/chemsoc/timeline//pages/1911.html
 * Ernest Rutherford published his atomic theory describing the atom as having a central positive nucleus surrounded by negative orbiting electrons. Rutherford came to this conclusion following the results of his gold foil experiment. The experiment consisted of the firing of radioactive particles through minutely thin metal foils (notably gold) and detecting them using screens coated with zinc sulfide. Rutherford found that although the vast majority of particles passed straight through the foil approximately 1 in 8000 were deflected leading him to his theory that most of the atom was made up of 'empty space'.




 * Robert Millikin**




 * Born: March 22, 1868 – December 19, 1953
 * Country of Origin: United States of America

> http://www.juliantrubin.com/bigten/millikanoildrop.html >
 * In 1909, Millikin started work on the oil-drop experiement. This measured the charge on a single electron. It was the first successful scientific attempt to detect and measure the effect of an individual subatomic particle. Millikan repeated the experiment numerous times. Each time he did it, he varied the strength of the x-rays ionizing the air. He did this so that differing numbers of electrons would jump onto the oil molecules each time.


 * Niels Bohr**




 * Born: 7 October 1885 – 18 November 1962
 * Country of Origin: Denmark

http://en.wikipedia.org/wiki/Image:Bohr-atom-PAR.svg
 * Bohr's atomic theory states that:
 * Electrons can only occupy certain orbits or shells in an atom. Each orbit represents a definite energy for the electrons in it.
 * Light is emitted by an atom when an electron jumps from one of its allowed orbits to another. Since each orbit represents a definite electron energy, this electron jump, or transition, represents definite energy jump. This change in electron energy leads to emission of light of a definite energy or wavelength.
 * Bohr's atomic model shows the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbit around the nucleus. The model was introduced in 1913. His model is a primitive model of a hydrogen model. Bohr model is still commonly taught to introduce students to quantum mechanics, before moving on to the more accurate but more complex valence shell atom.




 * Erwin Rudolf Josef Alexander Schrödinger**




 * Born: 12 August 1887 – 4 January 1961
 * Country of Origin: Austria-Hungary

http://wiki.answers.com/Q/Which_atomic_model_did_erwin_schrodinger_create
 * Schrödinger's wave equation was based on the Heisenberg uncertainty principal that the position and velocity of a electron cannot be determined accurately (accuracy in one will sacrifice accuracy in another). Schrödinger's wave equation gave a wave function, which squared gave the probability cloud of electrons. Therefore, Schrödinger's contribution resulted in the electron cloud model of the atom.




 * Werner Heisenberg**




 * Born: 5 December 1901 –1 February 1976
 * Country of Origin: Germany

http://www.infoplease.com/ce6/people/A0823222.html
 * One of the founders of the quantum theory, he is best known for his uncertainty principle, or indeterminacy principle, which states that it is impossible to determine with arbitrarily high accuracy both the position and momentum (essentially velocity) of a subatomic particle like the electron. The effect of this principle is to convert the laws of physics into statements about relative probabilities instead of absolute certainties. In 1926, Heisenberg developed a form of the quantum theory known as matrix mechanics, which was quickly shown to be fully equivalent to Erwin Schrödinger's wave mechanics. His 1932 Nobel Prize in Physics cited not only his work on quantum theory but also work in nuclear physics in which he predicted the subsequently verified existence of two allotropic forms of molecular hydrogen, differing in their values of nuclear spin.




 * James Chadwick**




 * Born: 20 October 1891 – 24 July 1974
 * Country of Origin: England

http://www.thocp.net/biographies/chadwick_james.htm
 * James Chadwick was a prisoner of war for four years during WWII. His main research in the labs was radioactivity. While they studied this, they realized over and over again that the atomic number was less than the atomic mass. While working with Rutherford on the experiment, they put out the idea that there could be a particle with a mass but no charge. They called this a neutron. After doing more experiments, they discovered that the neutron did exist and that its mass was about 0.1% more than a protons.