Fall.2008.MMA.Cavicchi.Timeline



Called nature’s basic particle an atom, based on the Greek meaning “invisible”. His view was not supported by evid\ence so his ideas were not thought to be true. Later, Dalton turned Democritus’ ideas into a scientific theory.
 * Democritus**

Joseph Priestley born in England on March 13, 1733 died on February 6, 1804.

Discovery’s 5. and observed photosynthesis for the first time.
 * 1) · graphite conducts electricity
 * 2) · isolated and described the properties of carbon dioxide, nitrous oxide, and oxygen,
 * 3) · invented soda pop,
 * 4) · identified the gases involved in plant respiration (unifying chemistry and biology),

(Priestley's air experiment)

John Dalton – Born on September 6, 1766 in Cumberland, England. Died on July 27, 1844 1808 he proposed a theory that explained the law of conservation of mass, law of definite proportions, and the law of multiple proportions. Called Dalton’s atomic theory Dalton's atomic theory: 1. All matter is composed of extremely small particles called atoms 2. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass and other properties. 3. Atoms cannot be subdivided, created or destroyed. 4. Atoms of different elements combine in simple whole number ratios to form chemical compounds.

Ernest Rutherford- Born on August 30, 1871 in Nelson New Zealand. Died on October 19, 1937. With Hans Geiger and Ernest Marsden, shot alpha particles at a thin, gold foil. They expected the alpha particles to pass through the foil with slight deflection because the charge was evenly distributed through the foil. They found out that 1 out of 8000 of the alpha particles had been redirected toward the source. This resulted in the conclusion that atoms had a solid nucleus. He suggested that electrons surrounded the nucleus, but he had no evidence to prove it.



J.J. Thompson- Born on December 18, 1856 in Cheetham Hill. In 1897 carried out a series of investigations on hypotheses on cathode rays. His experiment revealed that the electron has a very large charge for its tiny mass. He supported the ideas that cathode rays were deflected by a magnetic field in the same manner as a wire carrying electric current which was known to have a negative charge. And also that the rays were deflected away from a negatively charged object





Niels Bohr – Born October 7, 1885 in Copenhagen. Died on November 18, 1962 in Copenhagen. 1913 – He proposed a model of the hydrogen atom that linked the atoms electron with photon emission. According to the model, the electron can circle the nucleus only in allowed paths, or orbits, allowing the atom to have a definite, fixed energy. When hydrogen atom is in an excited state its electron is in a higher-energy orbit, until it falls back from the excited state to a lower-energy orbit, in the process a photon is emitted that has energy equal to the energy difference from the higher-energy level to the lower-energy level. While in orbit, the electron can neither gain nor lose energy. Bohr’s approach did not explain the spectra of atoms with more than one electron though. Also it did not explain the chemical behavior of atoms. In 1922, he received the Nobel Prize in recognition of his work on the structure of atoms



Wilhelm C. Roentgen Born on March 27, 1845 in Lennep. Died on February 10, 1923. In 1895, Roentgen discovered X-rays. X-rays are produced by the impact of cathode rays on a material subject. In 1901 he got the Noble prize for his work. Later, Max von Laue showed that x-rays are of the same electromagnetic nature as light, but differ from it only in higher frequency of their vibration





Henri Becquerel- Born on December 15, 1852 in Paris. Died on August 25, 1908. Found that he did not need sunlight to expose x-rays. By using a photographic plate wrapped in lightproof covering and by placing uranium compound on top of it without any sunlight the rays were still exposed. This proved that the rays were produced by radioactive decay. He was awarded ½ of the noble prize for physics in 1903 because of his discovery of spontaneous radioactivity



Marie Curie Born on November 7, 1867 in Warsaw. Died on July 4, 1934 in Savoy, France In 1896, with help of Pierre Curie, she found that out of all the elements known in that time, only Uranium and Thorium were radioactive. Then in 1898, the two discovered 2 more radioactive elements, polonium and radium. In 1903, they received half of the Noble Prize for this discovery





Wilhelm Wein Born on January 13, 1864. Died August 30, 1928. 1887 – experimented on the permeability of metals, light, and heat rays. In 1893- he announced the law which states that the wavelength changes with the temperature, a law which later became the law of displacement. In 1911 he was awarded with the Noble Prize for providing a formula for the composition of radiation in short waves.



Svante August Arrhenius ** born on February 19, 1859, died October 2, 1927, The Nobel Prize in Chemistry 1903 “From his results the author concluded that electrolytes, when dissolved in water, become to varying degrees split or dissociated into electrically opposite positive and negative ions.”



Robert A. Millikan Born on March 22, 1868 in Morrison, Ill. Died on December19, 1953 in San Marino, California. 1909 - His experiments showed that the mass of the electron is about one two-thousandth the mass of a hydrogen atom. His experiments also confirmed that electron carries a negative charge. Also, because cathode rays have have identical properties, regardless of the element used to produce them. The cathode ray experiments provided evidence that atoms are divisible and that one of the atoms basic units is the electron.

Max Planck- Born on April 23, 1858 in Germany. Died on October 4, 1947 Planck was able to deduce the relationship between the energy and the frequency of radiation. This marked a turning point in the history of physics. But the discovery wasn’t appreciated at first. It eventually became overwhelming as its applications accounted for many discrepancies between observed phenomena and classical theory. Was awarded the Nobel Prize in physics in 1918 for his discovery



Werner Heisenberg (German) Born December 5, 1901 in Wurzburg. 1925 – came up with one of the first and most used formulas in quantum mechanics. 1927 - Came up with the **Heisenberg Uncertainty Principle**: states that it is impossible to determine simultaneously both position and velocity of an electron or any other particle It has been proven to be one of the fundamental principles of our present understanding of light and matter Awarded the Noble Prize in 1932 for the discovery of allotropic forms of hydrogen.



Erwin Schrodinger Born on August 12, 1887 in Vienna. Died on January 4, 1961. 1926 – used the hypothesis that electrons have a dual wave-particle to develop an equation that treated electrons as waves. Along with the Heisenberg uncertainty principle, the Schrodinger wave equation laid the foundation for the modern quantum theory.



James Chadwick- Born on October 20, 1891 Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence of neutrons - elementary particles devoid of any electrical charge. Also prepared the way for the fission of Uranium 235 and towards the creation of the atomic bomb. For this dixcovery, Chadwick won the Noble Prize in 1935.





Conrad Weygand Born in 1890. Died in 1945. 1938- he came up with a way to classify chemical reactions based on bond breakage and formation during the reaction.



Glenn Seaborg Born on April 19,1912 in Ishpeming, Michigan. Died on February25, 1999. 1942-1946 headed the plutonium work for the Manhattan Project. He was a co-discoverer of plutonium and further transuranium elements through element 102. Identified more than 100 isotopes of elements on the periodic table. The information found by Seaborg made it possible to predict the radioactive characteristics of many isotopes still to be found (Manhattan project)

**Major World Events**
295 B.C. – Library of Alexandria built 269 B.C. – Rome begins exerting power over other Mediterranean countries 214 B.C. – Construction of the 2,500 mile Great Wall of China begins
 * __Ancient__**


 * __500-1800__**
 * 1066** William the Conqueror led the Normans of France to conquer England.
 * 1130** The Church banned bows and crossbows as immoral weapons not to be used against Christians
 * 1300** Gunpowder becomes widely used in siege machines

civil war sarted California Gold Rush begins. Pioneering women's rights convention
 * __1800-1875__**

Mass maritime was started  The first zeppelin test flight was conducted.  "Mickey Mouse" creator Walt Disney was born.
 * __1875-1900__**

Great automobile race from New York City to Pittsburgh Panama canal completed
 * __1900-1915__**

world war two. Establishment on the US Air force St. Valentine's Day massacre Vietnam 911 attacks financial crisis
 * __1915-1950__**
 * __1950-Current__**



The Plum Pudding Model was created by JJ Thomson. Its main perpuse was to show that the atoms are made of electorn souronded by positive charged.

http://en.wikipedia.org/wiki/Plum_pudding_model