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HISTORY OF THE PERIODIC TABLE

HISTORY OF THE PERIODIC TABLE. Johann Dobereiner. First noticed similarities among certain elements in 1829 Similar elements seemed to appear in groups of three Dobereiner’s Triads: ex. Cl, Br, I and Li, Na, K]. John Newland.

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HISTORY OF THE PERIODIC TABLE

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  1. HISTORY OF THE PERIODIC TABLE

  2. Johann Dobereiner • First noticed similarities among certain elements in 1829 • Similar elements seemed to appear in groups of three • Dobereiner’s Triads: ex. Cl, Br, I and Li, Na, K]

  3. John Newland • Arranged known elements in order of increasing atomic mass in 1864 • Noticed similar chemical and physical properties • Newland’s Law of Octaves • Problem: table had no gaps and therefore left no room for new elements

  4. Dimitri Mendeleev • Discovered periodic law in 1869 with Lothar Meyer but Mendeleev published his ideas first • Elements arranged in order of increasing atomic mass • Elements with similar properties recur at regular intervals • Gaps in the periodic table would later be filled by newly discovered elements (ie. Ga and Sc filled two of the gaps after they were discovered • Predicted properties of elements before they wer discovered

  5. Lord Rayleigh & William Ramsay • Caused periodic table to be modified by the discovery of Ar (noble gas) in 1894

  6. A. Van den Brock • Suggested in 1911 that the periodic table be arranged according to atomic number instead of atomic mass and thus eliminate several minor inconsistencies. • Example: according to atomic mass only, some elements appeared in the wrong column of the table, ie. Ar

  7. Henry Mosely • In 1913, confirmed that the properties of elements depend on atomic number rather than atomic mass • RESULT: Our modern periodic table today

  8. Periodic Law • When elements are arranged in order of increasing atomic number, elements with similar chemical and physical properties occur at regular intervals.

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