Question

Elements have been arranged in the following sequence on the basis of their increasing atomic masses. F, Na, Mg, Al, Si, P, S, Cl, Ar, K

(a) Pick two sets of elements that have similar properties.

(b) The given sequence represents which law of classification of elements?

Answer 1

(a) Elements with similar properties

• The chemical properties of elements are based on the number of electrons in their valence shell as they are the ones taking part in chemical reactions. Thus elements of a particular group have similar properties.
• Florine $\left(\mathrm{F}\right)$and chlorine $\left(\mathrm{Cl}\right)$are belonging to the halogen family and show similar properties. Both of them are group 17 elements and elements of a single group have similar properties.
• Sodium $\left(\mathrm{Na}\right)$and Potassium$\left(\mathrm{K}\right)$belonging to alkali metals show similar properties

(b) Law of classification of elements: Newlands octave: if the chemical elements are arranged according to increasing atomic weight, those with similar physical and chemical properties occur after each interval of seven elements.

Example of Newland octave series: F, Na, Mg, Al, Si, P, S, Cl, Ar, K.