Write an essay on the differences between lithium and other alkali metals.

Explanation

The anomalous behaviour of lithium is due to the : (i) exceptionally small size of its atom, and ion, and (ii) high polarsing power (i.e., charge`//`radius ratio). As a result, there is increased covalent character of lithium compounds which is responsible for their solubility in organic solvents.
Some of the abnormal properties of lithium are given below.
(i) Lithium is much harder.
(ii) Lithium is least reactive but the strongest reducing agent among all the alkali metals. On combustion in air it forms mainly monoxide . `Li_(2)O` and the nitride, `Li_(3)N`, unlike other alkali metals.
(iii) LiCl is deliquescent and crystallises as a hydrate, `LiCl.2H_(2)O` whereas other alkali metal chlorides do not form hydrates.
(iv) Lithium hydrogencarbonate is not obtained in the solid form while all other elements form solid hydrogencarbonates.
(v) Lithium unlike other alkali metals forms no ethynide on reaction with ethyne.
(vi) Lithium nitrate when heated gives lithium oxide, `Li_(2)O`, Whereas other alkali metal nitrates decompose to give the corresponding nitrites.
`4LiNO_(3) to 2Li_(2)O + 4 NO_(2) + O_(2)`
(vii) LiF and `Li_(2)O` are comparatively much less soluble in water than the corresponding compounds of other alkali metals.