Question

The atomic masses of three elements X, Y and Z having similar chemical properties are 7, 23 and 39 respectively.

(a) Calculate the average atomic mass of elements X and Z.

(b) How does the average atomic mass of elements X and Z compare with the atomic mass of element Y ?

(c) Which law of classification of elements is illustrated by this example ?

(d) What could the elements X, Y and Z be ?

(e) Give another example of a set of elements which can be classified according to this law.

Answer 1

(b) The average atomic mass of elements X and Z is equal to the atomic mass of element Y .

(c) Dobereiner’s law of triads.

(d) X is lithium, Y is sodium and Z is potassium .

(e) Chlorine, Bromine, Iodine .