Class 11 Chemistry The S Block Elements Anomalous properties of lithium

Anomalous properties of lithium

Anomalous behaviour of an element refers to the deviation of the properties and behaviour of an element from its usual or normal behaviour.

 It is due to the following reasons:

(i) Exceptionally small size of its atom and ion

(ii) High polarizing power

The anomalous behaviour of lithium is as follows:

  • Lithium is harder than other metals of the respective group.
  • It has higher Melting and boiling point than other metals
  • It is least reactive.
  • It is strongestreducing agent.
  • Unlike other metals LiCl is deliquescent and exist as LiCl.2H2
  • Li+ ion polarizes water molecules readily than other alkali metals of the respective group and hence the lithium salts attracts the water molecules and it exists as water of crystallization (2H2O). As the polarizing power decreases with the increasing size of the ions the other alkali metal ions usually form anhydrous salts.
  • Lithium does not form ethynide on reacting with Ethyne.
  • Heating lithium nitrate results in the production of lithium oxide, Li2

4LiNO3 --> 2Li2O + 4NO2 + O2

Lithium nitrate          Lithium oxide

  • Heating nitrates of other alkali metal results in the decomposition of the nitrate leading to the production of their corresponding nitrite.

2NaNO3 --> 2NaNO2 + O2

Sodium nitrate                  Sodium nitrite

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