Question

What was Döbereiner’s method of elemental classification? Illustrate with an example.

What were the drawbacks in his proposal?​

Answer 1

Answer: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.

Explanation:

drawbacks of Dobereiner’s classification:

 Dobereiner could find only three triads; .i.e total of 9 elements only. However the total number of elements were more than that of those encompassed in Dobereiner’s Triad.Thus, Dobereiner’s could not be classify most of the elements known at that time.

Answer 2

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1. Dobereiner use the property of increasing atomic mass of elements. He classify three elements together having similar properties and called it as triads. For example, the elements having lower atomic mass are placed before than elements having higher atomic mass.

2. Limitations of Dobereiner’s classification:

• Dobereiner could find only three triads; .i.e total of 9 elements only.
• However the total number of elements were more than that of those encompassed in Dobereiner’s Triad.
• Thus, Dobereiner’s could not be classify most of the elements known at that time.