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.
(a) Average atomic mass
= \(\frac{Mass\;o + X + Mass\;o +\;Z}{2}\)
= \(\frac{7+39}{2}\)
= 23
(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