Question

Can the following groups of elements be classified as Döbereiner's triad?

1. Na, Si, Cl
2. Be, Mg, Ca

Atomic mass of Be 9; Na 23; Mg 24; Si 28; Cl 35; Ca 40 Explain by giving reason.

Answer 1

1.  For set a, even though silicon's atomic mass is similar to the arithmetic mean of the atomic masses of sodium and chlorine. The physical properties of the elements are not similar. Hence, sodium, silicon and chlorine are not dobereiner's triad.
2. For set b, if the arithmetic mean of the atomic masses of beryllium and calcium is taken it is similar to the atomic mass of magnesium and the physical properties of the three elements are similar. So, Beryllium, magnesium and calcium can be classified as dobereiner's triad.