Question

State one achievement of classification of elements by the Law of Triads.

Answer 1

One achievement of classification of elements by the Law of Triads:

• Dobereiner's law of Triads was the first attempt to classify elements into a group of elements known at that time.
• It showed that elements can be classified in one way or the other which ultimately led to the more accurate classification in subsequent attempts by other scientists.

Dobereiner's Law of Triads:

• Dobereiner arranged the elements in a group of three (tri meaning three) elements.
• The group of three elements was made such that the atomic mass of the middle element of the triad was approximately equal to the arithmetic mean (average) of the atomic masses of the other two elements of that triad when arranged in their increasing order of atomic mass.
• This law was proposed by a German chemist called Johann Wolfgang Dobereiner in 1817.

Examples:

• Triad of Lithium, Sodium, and Potassium:

Elements of the triad arranged in the increasing atomic mass	Atomic mass (u)
Lithium (Li)	6.9
Sodium (Na)	23.0
Potassium (K)	39.0