2 some tables include an element zero ie a substance

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2. ^ Some tables include an element zero (i.e. a substance composed purely of neutrons), although this is uncommon. See, for example. Philip Stewart's Chemical Galaxy. 3. ^ The noble gases, astatine, francium, and all elements heavier than americium were left out as there is no data for them. 4. ^ While fluorine is the most electronegative of the elements under the Pauling scale, neon is the most electronegative element under other scales, such as the Allen scale. 5. ^ An antecedent of Deming's 18-column table may be seen in Adams' 16-column Periodic Table of 1911 (http://www.meta- synthesis.com/webbook/35_pt/pt_database.php?PT_id=67). Adams omits the rare earths and the 'radioactive elements' (i.e. the actinides) from the main body of his table and instead shows them as being 'careted (http://en.wiktionary.org/wiki/caret) in only to save space' (rare earths between Ba and eka-Yt; radioactive elements between eka-Te and eka-I). See: Elliot Q. A. (1911). "A modification of the periodic table". Journal of the American Chemical Society. 33 (5): 684–688 (687). 6. ^ A second extra-long periodic table row, to accommodate known and undiscovered elements with an atomic weight greater than bismuth (thorium, protactinium and uranium, for example), had been postulated as far back as 1892. Most investigators, however, considered that these elements were analogues of the third series transition elements, hafnium, tantalum and tungsten. The existence of a second inner transition series, in the form of the actinides, was not accepted until similarities with the electron structures of the lanthanides had been established. See: van Spronsen, J. W. (1969). The periodic system of chemical elements. Amsterdam: Elsevier. p. 315–316, ISBN 0-444-40776-6. 7. ^ See The Internet database of periodic tables (http://www.meta-synthesis.com/webbook//35_pt/pt_database.php) for depictions of these kinds of variants. 8. ^ The animated depiction of Giguère's periodic table that is widely available on the internet (including from here (http://101- 365.com/periodic/giguere.html)) is erroneous, as it does not include hydrogen and helium. Giguère included hydrogen, above lithium, and helium, above beryllium. See: Giguère P.A. (1966). "The "new look" for the periodic system". Chemistry in Canada 18 (12): 36–39 (see p. 37). 9. ^ Karol (2002, p. 63) contends that gravitational effects would become significant when atomic numbers become astronomically large, thereby overcoming other super-massive nuclei instability phenomena, and that neutron stars (with atomic numbers on the order of 10 21 ) can arguably be regarded as representing the heaviest known elements in the universe. See: Karol P. J. (2002). "The Mendeleev–Seaborg periodic table: Through Z = 1138 and beyond". Journal of Chemical Education 79 (1): 60–63. References 1. ^ Greenwood, pp. 24–27
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6/2/13 11:44 AM Periodic table - Wikipedia, the free encyclopedia Page 14 of 17 http://en.wikipedia.org/wiki/Periodic_table 2. ^ Gray, p. 6 3. ^ a b c d e f Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements (New ed.). New York, NY: Oxford University Press.
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