periodic table

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The periodic table of the elements. See Appendix:Chemical elements.

The table is termed “periodic” because it follows the periodic law – when chemical elements are arranged in order of increasing atomic number, elements with similar properties recur at intervals.



periodic table (plural periodic tables)

  1. (chemistry) A tabular chart of the chemical elements according to their atomic numbers so that elements with similar properties are in the same group (column).
    • 1903 March 26, William Ramsay, “[Societies and Academies. London.] An Attempt to Estimate the Relative Amounts of Krypton and of Xenon in Atmospheric Air.”, in Nature: A Weekly Illustrated Journal of Science, volume 67, number 1746, London; New York, N.Y.: Macmillan and Co., published 16 April 1903, OCLC 64051812, page 573, column 2:
      The atomic weight of krypton would accordingly be 81.62; the mean of former determinations is 81.28. This is in accordance with its position in the periodic table, which lies between bromine, 80, and rubidium, 85.
    • 1924, Frank Wigglesworth Clarke; Henry Stephens Washington, “Evolution of the Elements”, in The Composition of the Earth’s Crust (United States Geological Survey Professional Paper; 127), Washington, D.C.: Government Printing Office, OCLC 595215791, pages 107–108:
      Silica and alumina are distinctly the most abundant and characteristic petrogenic constituents, and with them are most frequently associated those elements toward the extreme petrogenic end of the periodic table, especially potassium, sodium, and calcium in the order named; and these elements are associated with each other.
    • 1977 June, George N. Bowers, “Introduction—The Gallium Melting-point Standard: A New Fixed Point to Assure the Accuracy of Temperature Measurements in the Clinical Laboratory”, in B[illy] W[ilson] Mangum and D[onald] D. Thornton, editors, The Gallium Melting-point Standard (National Bureau of Standards Special Publication; 481), Washington, D.C.: U.S. Government Printing Office, OCLC 758253357, page 709, column 1:
      Gallium, the 32nd most abundant element in the earth's crust, is a silver-grey metal, widely distributed in trace amounts in many rocks and ores. Its name, gallium (Lat., gallia, France), honors the discovery of this element by a French chemist in 1875, just four years after [Dmitri] Mendeleev predicted its probable existence from a blank space in his newly described periodic table.
    • 1983 spring, Richard Hahn, “Life at the End of the Periodic Table”, in Carolyn Krause, editor, Oak Ridge National Laboratory Review, volume 16, number 2, Oak Ridge, Tenn.: Oak Ridge National Laboratory, ISSN 0048-1262, OCLC 224131947, page 25, column 1:
      The main theme of TRL [Transuranium Research Laboratory] research with transuranium elements has been the exploration of a region of the periodic table that is relatively new and inaccessible to most scientists. [] Our research with the heavy elements has extended our knowledge considerably and tested our ideas concerning how the periodic table is constructed.
    • 2009, Kristi Lew, “Mercury: The Inside Story”, in Mercury (Understanding the Elements of the Periodic Table), New York, N.Y.: The Rosen Publishing Group, →ISBN, page 20:
      Taking into account the masses and percents of the isotopes, the average weight of a mercury atom is 200.59 amu, the atomic weight that is listed on some periodic tables. This type of average is called a weighted average. On other periodic tables, such as the one in this book, mercury's atomic weight is rounded to the nearest whole number (201 amu).
    • 2015, Peter J. Mikulecky; Christopher Hren, “Understanding the Many Uses of the Mole”, in Chemistry Workbook for Dummies, 2nd edition, Hoboken, N.J.: John Wiley & Sons, →ISBN, part II (Making and Remaking Compounds), page 101:
      The atomic masses you see in many periodic tables may vary slightly, so for consistency, we've rounded all atomic mass values to two decimal places before plugging them into equations.

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