SCIENCE
PHYSICAL SCIENCES
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The atomic mass of the first element in the triad is the approximate mean of the atomic masses of the second and third elements.
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The atomic mass of the second element in the triad is the approximate mean of the atomic masses of the first and third elements.
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The atomic mass of the third element in the triad is the approximate mean of the atomic masses of the first and second elements.
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None of the above
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Detailed explanation-1: -According to Dobereiner’s triads, the atomic mass of the 2nd element is equal to the of 1st and 3rd elements in that triad.
Detailed explanation-2: -Dobereiner’s triad was discarded because it failed to arrange all the known elements in the form of triads.
Detailed explanation-3: -According to Dobereiner, elements having similar properties can be arranged in triads in which mass of the middle element is the mean of the atomic masses of the other two elements.
Detailed explanation-4: -Solution : He classified in group of three such that atomic No. of middle elements is average of first and third element. Eg: Li(7), Na(23), K(39), Limitations : <br> * Dobereiner could find only three triads, i.e. total of 9 elements only.
Detailed explanation-5: -Dobereiner’s triads had a great significance in predicting atomic mass and properties of middle element. II. Law of Octaves is based upon octaves found in music.