Question

Can these group of elements be classified as Dobereiner's triads ? Explain your answer.


Be , Mg , Ca

N , O , F

Answer 1

These elements cannot be classified under Dobereiner's triads , as when the elements are arranged in the increasing order of their atomic masses, the atomic masses of the middle most element is not the average of the other two elements

Answer 2

Answer:

No, these groups of elements cannot be classified as Dobereiner’s Triads.

Explanation:

The law of triads states that when the elements are arranged in the increasing order of their atomic masses, then the arithmetic mean of the first and third element’s atomic masses should be equivalent to the atomic mass of the second element in the triad.

1). Be, Mg, Ca -

The atomic mass of Be = 9.012 amu

The atomic mass of Ca = 40.078 amu

= (9.012+40.078)/2 = 24.545 amu

But the atomic mass of Mg is 24.305 amu

2). N, O, F -

The atomic mass of N = 14.007 amu

The atomic mass of F = 18.998 amu

= (14.007+18.998)/2 = 16.5025 amu

But the atomic mass of O is 15.999 amu

In both cases, the atomic mass of the second element is not the arithmetic mean of the first and third element’s atomic masses.

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