What name did Dobereiner give to his groups of three similar elements?

Correct option is B

The correct answer is (b) Triads
Explanation:
· Johann Wolfgang Dobereiner, a German chemist, classified some elements into groups of three, based on similarities in chemical properties—these groups were called Triads.
· In each triad, the atomic mass of the middle element was approximately the average of the masses of the other two.
· This was the earliest scientific attempt at Periodic Classification, forming the base for later scientists like Newlands and Mendeleev.
· NCERT (Class 10 Science, Chapter: Periodic Classification of Elements) mentions Dobereiner’s Triads as the first systematic classification effort in chemistry.
Information Booster:
· Examples of famous Triads:
· Li – Na – K
· Cl – Br – I
· Ca – Sr – Ba
· Only a few elements could be arranged into Triads because many atomic masses were not known accurately in that era.
· Triads displayed periodicity in atomic mass, reactivity, and valency.
Additional Knowledge:
(a) Triangles
Incorrect — no such classification exists in chemistry.
(c) Triplets
Incorrect — although triads are groups of three, the formal scientific term is Triads.
(d) Triodes
Incorrect — triode is an electronic vacuum tube, not related to elements.