Home ยป The third member of the Dobereiner triad consisting of lithium and sodium is Periodic Table MCQs The third member of the Dobereiner triad consisting of lithium and sodium is April 16, 2022 6 Views Q. The third member of the Dobereiner triad consisting of lithium and sodium is : A. Potassium B. Hydrogen C. Boron D. Barium Answer: Potassium