How many triads were mentioned in Dobereiner's Triads?

Correct option is D

The correct answer is Four.
Dobereiner's Triads were groups of three elements arranged by Johann Wolfgang Döbereiner, where the atomic mass of the middle element was approximately the average of the other two elements. While Döbereiner initially identified a few triads, there were four recognized triads that are widely accepted in chemistry.
· These triads were:
1. Lithium (Li), Sodium (Na), Potassium (K)
2. Calcium (Ca), Strontium (Sr), Barium (Ba)
3. Chlorine (Cl), Bromine (Br), Iodine (I)
4. Sulfur (S), Selenium (Se), Tellurium (Te)
Information Booster:
· Dobereiner's Triads demonstrated a relationship between the atomic weights and chemical properties of elements, where the atomic weight of the second element was approximately the average of the first and third.
· This was an early precursor to the modern Periodic Table, which arranges elements based on their atomic number.
· The concept of triads did not apply to all known elements and had limitations, but it paved the way for the future classification of elements.
· John Newlands later proposed the Law of Octaves, and Dmitri Mendeleev developed the first version of the modern periodic table based on atomic weights.