Question

Question:-

Explain in brief about Dobereiner 's Triads .

Note;-

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Answer 1

Explanation:

• German Scientist Johan Wolfgang Dobereiner Had started classification of Elements in 1817.
• He had made 3 sets of Elements known as Dobereiner's Triads.

Dobereiner's Triads:-

$\boxed{\begin{array}{c|c|c}\sf Li &\sf Ca &\sf Cl \\&&\\ \sf Na &\sf Sr &\sf Br \\&&\\ \sf K &\sf Ba &\sf I \end{array}}$

Classification:-

• In each triads the average of the Atomic masses of 1st and 3rd element is equal to the atomic mass of 2nd element .

Example:-

$\sf Atomic\: mass\:of\:Calcium=40.1$

$\sf Atomic\: mass\:of\:Strocium =87.6$

$\sf Atomic\: mass\:of\:Barium=137.3$

$\sf Average\:of\:Calcium\:and\:Barium=\dfrac{40.1+137.3}{2}=\dfrac{177.4}{2}=88.7$

• It is approximately equal to Atomic mass of Strocium.

Answer 2

Answer:

Explanation:

Dobereiner arranged the element in increasing order of atomic masses. He found that the atomic mass of the middle element was approximately equal to the arithmetic mean (average) of the atomic masses of the other two elements of that triad when they are arranged in their increasing order of atomic mass,

e.g., Li, Na, K. The atomic mass of Li is 9 and K is 39. The average of two atomic number is 23 that is the atomic number of sodium.

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.  

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.

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