Question

Which of the following set of elements do not form a Döbereiner’s triad?

• A. Carbon, nitrogen, and oxygen
• B. Calcium, strontium, and barium
• C. Bromine, chlorine, and iodine
• D. Lithium, sodium, and potassium

Answer 1

The correct option is A Carbon, nitrogen, and oxygen

Döbereiner arranged elements in triads such that

• The atomic mass of the middle element is roughly the average of the atomic masses of the other two elements.
• The elements in triads possessed similar properties.

All of the given sets satisfy the first criteria i.e. atomic mass of the middle element is the average of atomic masses of the other two elements. But carbon, nitrogen, and oxygen do not possess similar properties. Hence, these elements do not form a Döbereiner’s triad.