Question

Given elements X, Y and Z with atomic masses a,b and c are said to form Dobereiner's triad. Which of the following statement is true if its known that a > b > c?

• A. $b\approx \frac{a-c}{2}$
• B. $b\approx 2a-c$
• C. $b\approx \frac{3c+a}{2}$
• D. $b\approx \frac{c+a}{2}$

Answer 1

The correct option is D

$b\approx \frac{c+a}{2}$

According to the Dobereiner's law of triads, the average of the atomic mass of the first and last elements of the triad will be equal to the atomic mass of the second element.

Given that a, b and c are the atomic masses of the elements X, Y and Z and we know that a > b > c.

So, $b\approx \frac{c+a}{2}$