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Periodic Table: Then and Now

Periodic Table: Then and Now. Garrick Hill Phys 6602 Dr. David Moore NGCSU. In the Beginning…. The first periodic table was published (in 1862) French geologist, A.E.Beguyer de Chancourtois.

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Periodic Table: Then and Now

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  1. Periodic Table: Then and Now Garrick Hill Phys 6602 Dr. David Moore NGCSU

  2. In the Beginning…. • The first periodic table was published (in 1862) French geologist, A.E.Beguyer de Chancourtois. • De Chancourtois transcribed a list of the elements positioned on a cylinder in terms of increasing atomic weight.

  3. An Early Proposal • When the cylinder was constructed so that 16 mass units could be written on the cylinder per turn, closely related elements were lined up vertically. • This led de Chancourtois to propose that "the properties of the elements are the properties of numbers."

  4. De Chancourtois’ Folley • De Chancourtois was first to recognize that elemental properties reoccur every seven elements, and using this chart, he was able to predict the stoichiometry of several metallic oxides. • Unfortunately, his chart included some ions and compounds in addition to elements.

  5. John Newlands • John Newlands, an English chemist, wrote a paper in 1863 which classified the 56 established elements into 11 groups based on similar physical properties, noting that many pairs of similar elements existed which differed by some multiple of eight in atomic weight.

  6. Name That Tune In 1864 Newlands published his version of the periodic table and proposed the Law of Octaves (by analogy with the seven intervals of the musical scale). This law stated that any given element will exhibit analogous behavior to the eighth element following it in the table.

  7. Mendeleev • In 1864 Russian chemist, Dmitri Mendeleev greatly improved on Newlands' idea and convinced other chemists to use it, so Mendeleev has been credited with the invention of the periodic table.

  8. Raleigh and Ramsey • The first major change to the periodic table occurred following the discovery of an entirely new group of elements, the noble gases, between 1895 and 1901. • They were called the noble gases because they were believed to be inert—incapable of reacting with other elements to form compounds.

  9. Noble, More or Less • These elements were simply added on in a separate column under helium. • Today it is known that they do enter into chemical combinations, only reluctantly.

  10. Positively Revised • The first major revision of the entire periodic table was carried out by Henry Gwyn-Jeffries Moseley, an English physicist. • In 1914, Moseley showed that each atomic nucleus could be assigned a number that was equal to the number of units of positive charge (later identified as “protons”) associated with it. • Once the periodic table was reorganized according to this atomic number instead of atomic weight, the few discrepancies in Mendeleev's system disappeared.

  11. Rare Earth • Over the years other revisions of the table have been made, including the incorporation of the rare-earth elements (lanthanide series) and the synthetic elements (technetium, promethium, and all the elements with atomic number 93 or higher).

  12. Out to Seaborg • Most of these changes were the work of American chemist Glenn Seaborg, who co-discovered elements 94 (plutonium) through 102 (nobelium) between 1940 and 1958.

  13. A Row Below • The actinides, which are radioactive and mainly synthetic, and the lanthanides do not fit into the same pattern of repeated properties as the other elements, so they are generally shown below the periodic table in separate rows.

  14. Seaborg Says • Seaborg also suggested a superactinide series of elements, with atomic numbers 122 through 153, but so far none of these has been synthesized or detected.

  15. No More Status Quo Since Mendeleev came up with his first version of the periodic table, since then more than 700 versions of the table have been proposed.

  16. The British Are Coming • The Royal Society of Chemists recently sent a copy of a new periodic table by Oxford ecologist Philip Stewart to every British secondary school. • Stewart's is the first remake to achieve widespread adoption

  17. Spurred Stewart • At 12, Stewart saw artist Edgar Longman’s work, and it spurred Stewart to study science. He recalls being struck by nature's underlying order: "I realized that the atoms that make up a galaxy can be arranged in just the same form as the galaxy itself."

  18. Why A Galaxy? Ask Stewart… • When the chemical elements are arranged in order of the increasing positive charge on the nucleus of the atom (and so of the increasing number of negative electrons in orbit around it), they form a continuous sequence, in which certain chemical characteristics, which depend mainly on the number of electrons, come back periodically in a regular way. This is usually shown by chopping the sequence up into sections and arranging them as a rectangular table. The alternative is to wind the sequence round in a spiral. Because the periodic repeats come at longer and longer intervals, increasing numbers of elements have to be fitted on its coils. Edgar Longman showed in 1951 that this is best done by making the spiral elliptical. In this new version, for the first time, the size of successive turns is made to increase at a constant rate. The resulting pattern resembles a galaxy, and the likeness is the basis of my design. It seems appropriate, as the chemical elements are what galaxies are made of (leaving aside the question of the mysterious ‘dark matter’).

  19. No Substitutions • The intention is not to replace the familiar table, but to complement it and at the same time to stimulate the imagination and to evoke wonder at the order underlying the universe.

  20. The last question…. • Can we continue to teach the traditional method along side alternative examples to help students understand?? • Enjoy: • http://www.privatehand.com/flash/elements.html

  21. References • Organizing the elements. Retrieved on October 05, 2007. http://www.3rd1000.com/history/periodic.htm • Is it time to revamp the periodic table? Jon Lackman Posted Tuesday, July 19, 2005. Retrieved October 09, 2007. Slate. http://slate.com/id/2122919?nav=wp • Chemical galaxy: technical notes. Phillip Stewart. Retrieved October 15, 2007. http://www.chemicalgalaxy.co.uk/technicalnotes.htm • Periodic table's design gets an elemental challenge. Michelle Lefort 7/26/2005 USA TODAY Retrieved October 09, 2007. http://www.usatoday.com/tech/science/2005-07-25-periodic-table_x.htm • A brief history of the development of the periodic table. Western Oregon University. Retrieved October 14, 2007. http://www.wou.edu/las/physci/ch412/perhist.htm

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