Category : 10th Class
In the year 1829, Johann Wolfgang Dobereiner, a German scientist, was the first to classify elements into groups based on John Dalton's assertions. He grouped the elements with similar chemical properties into clusters of three, called 'Triads'. The distinctive feature of a triad was the atomic mass of the middle element. When elements were arranged in order of their increasing atomic mass, the atomic mass of the middle element was approximately the arithmetic mean of the other two elements of the triad.
Elements | Atomic mass | Average Atomic Mass |
Lithium | 7 | |
Berellium | 9 | 9 |
Potassium | 11 |
Elements | Atomic mass | Average Atomic Mass |
Carbon | 12 | |
Nitrogen | 14 | 14 |
Oxygen | 16 |
Elements | Atomic mass | Average Atomic Mass |
Calcium | 40 | |
Strontium | 87.5 | 88.1 |
Barium | 11 |
Elements | Atomic mass | Average Atomic Mass |
Chlorine | 35 | |
Bromine | 80 | 80.6 |
Iodine | 127 |
Drawback of Triad Classification
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