Question

According to the law of triads, the properties of the middle element were in between those of the other two elements. This law was proposed by

• A. Dobereiner
• B. Dimitri Mendeleev
• C. Lothar Mayer
• D. Newlands
• E. Henry Moseley

Hint:

Think of "D-Triad" to associate Dobereiner with Triads.
"N-Octave" for Newlands and Octaves.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Early classification of elements was based on finding relationships between the physical and chemical properties of elements and their atomic weights.

Step 3: Detailed Explanation:
In 1817, the German chemist Johann Wolfgang Dobereiner suggested the "Law of Triads."
He identified groups of three elements (triads) with similar chemical properties.
He observed that when these elements were arranged in increasing order of their atomic masses, the atomic mass of the middle element was approximately equal to the arithmetic mean (average) of the atomic masses of the other two elements.
Example: Lithium (7), Sodium (23), and Potassium (39).
Average = \((7+39)/2 = 23\), which is the mass of Sodium.

Step 4: Final Answer:
The law of triads was proposed by Dobereiner.