Question

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Define Dobereiner Triad Rule . ♥️ ​

Answer 1

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. Example: In the triad of lithium, sodium and potassium. The 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: All the known elements could not be arranged in the form of triads. This law did not hold good for elements with very 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.

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Answer 2

$\huge\purple{♡}$$\large\underline\purple{\sf Dobereiner\:Traid\:Rule:-}$

$\large{♡}$He made group of three elements having similar chemical properties called TRAID.

$\large{♡}$In Dobereiner traid, atomic Weight of middle element is nearly equal to the average atomic Weight of first and third element.

1.Example :-

Cl ━ 35.5

Br ━ 80.0

I ━ 127

$\large{\sf x={\frac{35.5+127}{2}}}$

$\large\implies{\sf 81.2}$

2. Example :-

Ca ━ 40

Sr ━ 87.5

Ba ━ 137

$\large{\sf x={\frac{40+137}{2}}}$

$\large\implies{\sf 88.5}$

Here ,

x=Average atomic Weight.

Some other examples are :-

1. K, Rb, Cs

2. P, As, Sb

3. S, Se, Te