Donbereiner's Triads

   

          Johann Wolfgang Donbereiner

    Johann Wolfgang Donbereiner  a German scientist (1780 - 1849) studied as a pharmacist at Munchberg in Germany and then studied chemistry at  Strasbourg.  He later became professor of chemistry and pharmacy at the University of  Jena.

    In 1829 he found some groups of three elements which showed similar properties. These groups were called as a triads. ln this triads, atomic masses of the middle elements was approximately the mean of the atomic masses of the other two elements. Also these elements showed similarities in properties. The table below shows four triads arranged vertically. 

         In the above table, take the triads of Lithium, Sodium and Potassium. The Atomic mass of sodium (23) is the mean of the atomic masses of Lithium and Potassium.

    Similarly, you can verify the atomic masses of Strontium, Bromine and Selenium from the other triads.

    The triads were known as Donbereiner's Triads. 

    Donbereiner could identify only some triads  from the elements known other triads did not obey  Donbereiner's rule. Hence, the system of Triads was not useful.

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