What are the features of lithium which separates it from other elements of Group 1?
The following features separate lithium from the other elements of Group I:
(i) Lithium is the hardest of all the alkali metals.
(ii) The melting and boiling points of lithium are much higher than those of other elements of Group 1.
(iii) Lithium is less reactive as compared to other metals and it does not get tarnished readily in air.
(iv) It forms only monoxide, Li2O with oxygen while sodium forms peroxide-Na2O2; other elements form superoxide, MO2.
(v) Because of high polarizing power of Li+ ion, the salts of lithium have lower ionic character than salts of other alkali metals.
(vi) While other alkali metals do not react with nitrogen, lithium does, forming nitride.
(vii) Only lithium combines with carbon and silicon forming the carbide and the silicide.
(viii) Lithium hydroxide and carbonate are unstable and decompose on heating while the corresponding compounds of the rest of the family members are stable and do not decompose:
(ix) When lithium nitrate is heated it gives nitrogen dioxide and oxygen
(x) Sodium nitrate and potassium nitrate upon strong heating form corresponding nitrites and evolve oxygen.
(xi) Lithium chloride and nitrate are soluble in alcohol, while the salts of sodium are insoluble in alcohol.
(xii) The hydride of lithium (LiH) is more stable as compared to the hydrides of other members of the family.
(xiii) The Li+ ion and its compounds are more heavily hydrated than those of sodium.
(xiv) Lithium hydroxide is much less basic than the hydroxides of other metals.
(xv) Lithium fluoride, carbonate, hydroxide, oxalate are sparingly soluble in water. The corresponding salts of sodium and potassium are readily soluble.
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