neet exam 2022
The first classification of elements is attempted by
1. Dobereiner
2. Mendeleff
3. Mosley
4. John A.R. Newlands
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Triads means
1. Small groups of Three elements
2. Small groups of Four elements
3. Small groups of Five elements
4. Small groups of Six elements
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Dobereiner arranged elements as
1. groups
2. periods
3. triads
4. All the above
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Which of the following group of elements are triad
1. Na, Ne, k
2. Cl, Br, I
3. Li, Fe, Ni
4. C, N, O
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