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Dobereiner's Law of Triads

In this video you will Learn - Dobereiner's Law of Triads A triad is a grouping of three elements in order of atomic mass Dobereiner's law of triads states that, the atomic mass of the middle element of a triad is the arithmetic mean of the atomic masses of the other two elements.  In the history of the periodic table, Döbereiner's triads were an early attempt to sort the elements into some logical order by their physical properties. In 1817, a letter reported Johann Wolfgang Döbereiner's observations of the alkaline earths; namely, that strontium had properties that were intermediate to those of calcium and barium.[1] By 1829, Döbereiner had found other groups of three elements (hence "triads") whose physical properties were similarly related.[2] He also noted that some quantifiable properties of elements (e.g. atomic weight and density) in a triad followed a trend whereby the value of the middle element in the triad would be exactly or nearly predicted by taking the arithmetic mean of values for that property of the other two elements. Example:In the triad of lithium, sodium and potassium (Alkali-forming elements) Li - 6.9 Na - 23 K - 39.1 More example of Triad 1. Calcium, Strontium, Barium (Alkaline-earth-forming elements) 2. Chlorine, Bromine, Iodine (Salt-forming elements) 3. Sulphur, Selenium, Tellurium (Acid-forming elements) 4. Iron, Cobalt, Nickel Limitations of Dobereiner's classification of elements it failed to arrange all the then known elements in the form of triads of elements having similar chemical properties. His classification was not applicable to all known elements but was limited only to a few elements To Watch Video How to Memorize all 118 ELEMENTS in Periodic Table | Hindi    • How to Memorize all 118 ELEMENTS in Period...   Thank you very much!!! Take Care…