Identify the Dobereniers traid amond the following. 

According to Dobereiner'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 = 7 and the atomic mass of potassium = 39. The arithmetic mean of atomic masses of lithium and potassium gives atomic mass of sodium=23.