Question

Which of the following is a Döbereiner's triad?

• A. Ne, Ca, Na
• B. $H_2,N_2,O_2$
• C. Li, Na, K
• D. Cl, Na, Ca

Answer 1

The correct option is C

Li, Na, K

According to Döbereiner's law of triads, the atomic mass of the middle element of a triad is equal to the arithmetic mean of the atomic masses of the other two elements.

In the triad of lithium, sodium and potassium. The atomic mass of lithium is 7 and the atomic mass of potassium is 39. The arithmetic mean of atomic masses of lithium and potassium gives atomic mass of sodium i.e. 23.