Question

Chlorine, Bromine and Iodine form a Dobereiner’s triad. Chlorine has atomic mass 35.5 and Iodine has atomic mass 126.9. Predict the atomic mass of Bromine.

Answer 1

As chlorine (Cl), bromine (Br) and iodine (I) form a triad, atomic mass of Br should be the mean of atomic mass of Cl and I.

∴ Atomic mass of Br = \(\frac{35.5+126.9}2\) = 81.2

∴ Atomic mass of Br would be approximately 81 (actual mass is 79.9).