Justify the inclusion of alkali metals in the same group of the periodic table with reference to the following.
(i) Electronic configuration.

Explanation

i) Electronic configuration: All the alkali metals have one valence electrons `ns^-1`

(ii) Reducing nature
Alkali metals are strong reducing agents
Li is most powerful reducing agent and Na is poor reducing agent
The standard electrode potential `(E^@)` is the measure of reducing power.
Li has highest hydration enthalpy. It is high negative S.E.P `(E^@)` hence it has high reducing power.
(iii) Oxides and hydroxides:
The alkali metals forms their oxides in presence of dry air and tarnished.
These oxides reacts with moisture to form hydroxides
They burn vigorously in oxygen and forms oxides.
i) Lithium forms lithium monoxide
(ii) Sodium forms monoxide with limited supply of oxygen and peroxide with excess of oxygen. (iii) Other metals of this group forms super oxides. The super oxide ion `(O_2^-)` is stable only in presence of large cations.
Reactions:
`4Li+O_2 to 2Li_2O`
`4Na+O_2 (LImited) to 2Na_2O`
`2Na+O_2 (Excess) to Na_2O_2`
`K+O_2 (Excess) to KO_2`
Lithium shows a different character. It reacts directly with nitrogen of air and forms `Li_3N` (lithium nitride)
Alkali metals oxides easily hydrolysed by water to form the hydroxides.
Monoxide: `M_2O+H_2O to 2MOH`
Peroxide: `M_2O_2+ 2H_2O to 2MOH+H_2O_2`
Superoxide: `2MO_2+2H_2O to 2MOH+H_2O_2+ O_2`
Oxides, peroxides and colourless whereas superoxides are coloured because of their para magnetic property.
Hydroxides are white crystalline solids.
Hydroxides are strong bases and dissolved freely in water and evolve muc heat.