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What is doberneir triad |
Answer» According to Dobereiner, all elements occurred in groups of three, when arranged in increasing order of atomic masses. He referred to these groups as triads. In a traid the elements had similar chemical properties. Traids of the Dobereiners classification:\xa0Traid1:\t Element Atomic mass Lithium (Li) 7 Sodium (Na) 23 Potassium (K) 39\tTraid2:\t Element Atomic mass Chlorine (Cl) 35.5 Bromine (Br) 80 Iodine (I) 127\tTraid3:\t Element Atomic mass Calcium (Ca) 40 Strontium (Sr) 88 Barium (Ba) 137\tDobereiner’s law\xa0of triads\xa0states that, the\xa0atomic mass\xa0of the middle element of a triad is the\xa0arithmetic mean\xa0of the atomic masses of the other two elements. Example:\xa0In\xa0the triad of lithium, sodium and potassium.\xa0The atomic mass of lithium is 7 and the atomic mass of potassium is 39. The average of masses of lithium and potassium gives atomic mass of sodium 23. Drawbacks:\xa0All the\xa0known elements\xa0could not be arranged in the form of triads.\xa0This law did not hold good for elements with\xa0very low or very high atomic mass. Example: The arithmetic mean of the atomic masses of fluorine 19 and bromine 80, which comes to 49.5, varies significantly from the atomic mass of chlorine, which is 35.5.\xa0 |
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