Q4
Can the following groups of elements be classified as Dobereiner’s triad:
(a) Na, Si, Cl
(b) Be, Mg, Ca
Atomic mass of Be-9; Na-23, Mg-24, Si-28, Cl-35, Ca-40, Justify your answer in each case.
Solution
(a) Na, Si, Cl cannot be classified as Dobereiner’s triad because here the elements do not belong to the same group and have different electronic configuration.
Na – 2, 8, 1; Si – 2, 8, 4 and Cl – 2, 8, 7
(b) Be, Mg, Ca are the elements of Dobereiner’s triad because the mass of Mg is the arithmetic mean of the other two elements
i.e; Be and Ca = ( 9+40 ) / 2 = 24.