Question

In Dobereiner's triad, elements showed similarities in ___________.

Answer 1

The average Dobereiner's triad:-

• According to Dobereiner, three elements in a triad were arranged according to the increasing order of atomic masses.
• Then the atomic mass of the middle element was roughly the average atomic masses of the other two elements present in that triad.
• Dobereiner identified groups of three elements that had similar properties (called triads).
• For example:

Elements	$\mathrm{Li}\mathrm{Na}\mathrm{K}$	$\mathrm{Cl}\mathrm{Br}\mathrm{I}$	$\mathrm{Ca}\mathrm{Sr}\mathrm{Ba}$
Atomic masses	$72339$	$35.580127$	$4088137$
The average atomic mass of the first and third element	$\frac{7+39}{2}=23$	$\frac{35.5+127}{2}=81.25$	$\frac{40+137}{2}=88.5$

• But there was a major drawback in Dobereiner's triad.
• It was that all the elements which were discovered at that time could not be classified into triads.
• Only a limited number of elements were able to be arranged in such triads.

Therefore, in Dobereiner's Triad, elements showed similarities in properties.