“The properties of the elements are a periodic functions of their atomic number”. Justify the statement with suitable example.
There are various physical properties of elements such as melting points, boiling points, heats of fusion and vaporization, energy of atomisation etc., which show periodic variations. The cause of periodicity in properties is the repetition of similar outer electronic configuration after certain regular intervals, example, all the elements of Is group (alkali metals) have similar outer electronic configuration.
Li- 1s2, 2s1.
Na-1s2, 2s2, 2p6, 3s1.
K-2s2, 2s2, 2p6, 3s2, 3p6, 4s1.
Therefore, due to similar outermost shell electronic configuration all alkali metals have similar properties. e.g., sodium and potassium both are soft and reactivemetals.