Dobereiner's Triads

Johann Wolfgang Dobereiner , 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 triads. In these triads, atomic mass of the middle element was approximately the mean of the atomic masses of other two elements. also these elements showed similarities in properties.

 Element                           Atomic Mass

 1) Lithium (Li)                         6.9

 2) Sodium (Na)                         2.3

 3) Potassium (K)                       39

 1) Calcium (Ca)                       40.1

 2) Strontium (Sr)                     87.6

 3) Barium (Ba)                      137.3

           In the Above, take the triad 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 mass of strontium.

Questions on Periodic Table:-
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