Question

In the given periodic table the coloured boxes represents elements and are grouped as _______________

• A. Alkalies
• B. Halogens
• C. Dobereiner triads
• D. Noble gases

Answer 1

The correct option is C

Dobereiner triads

Dobereiner suggested a relationship between the properties of elements and their atomic weight. According to Dobereiner, the atomic weight, the atomic weight of the middle element is nearly the same as average of the atomic weight of other elements If we take Lithium ,Sodium and Potassium , the atomic weight of sodium is mean of the atomic weight of Lithium and Potassium $\frac{7+39}{2}=23$.The element that were grouped as triads are coloured.