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What is meant by Dobereiner's triads? Explain. |
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Answer» Solution :Johann Wolfgang Dobereiner, a German chemist tried to arrange the elements with similar properties into GROUPS. He identified some groups having THREE elements each. These groups of three elements were called triads. Law of triads : When the three elements in a triad were arranged in the order of INCREASING atomic masses, the atomic mass of the middle element is roughly the average of the atomic masses of the other TWO elements. For example, lithium (Li), SODIUM (Na) and potassium (K) constitute a triad. The atomic masses of Li, Na and Kare 6.9 u, 23.0 u and 39.0 u respectively. The atomic mass of middle element, sodium (Na) is roughly the average of the atomic masses of lithium (Li) and potassium (K).  Average of atomic masses of Li and `K=(6.9+39)/(2)=22.95~=23.0u` Dobereiner.s triads are as follows: 
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