PROPERTIES OF LITHIUM || ANOMALOUS PROPERTIES OF LITHIUM || Lithium ||

   ANOMALOUS PROPERTIES OF LITHIUM

The anomalous behaviour of lithium is due to the : (i) exceptionally small size of its atom and ion, and (ii) high polarising power (i.e., charge/ radius ratio ). As a result, there is a increase in covalent character of lithium compound which is responsible for their solubility in the organic solvent. Further, lithium shows diagonal relationship to magnesium. 

Atomic number                            3

Group                                             1 

Period                                             2

Block                                         s-block

Element category               Alkali metal

Electronic configuration      1s² 2s¹

Appearance                          Silvery-white

Melting point        453.65 K ​(180.50 °C, ​356.90 °F)

Oxidation state                                      +1

Atomic radius                             152 pm

Points of Difference between Lithium and other Alkali Metals are :

» Lithium is much harder. Its melting point and boiling point are higher than the other alkali metals.

» Lithium is least reactive but the strongest reducing agent among all the alkali metals. On combustion in air it mainly forms monoxide, as Li 2 O and the nitride, Li 3N unlike other alkali metals. 

» The lithium ion itself, and also its compounds are more heavily hydrated than those of the rest of the group. Li Cl is deliquescent and crystallises as a hydrate, Li Cl. 2H2O whereas other alkali metal chlorides do not form hydrates. 

» Lithium hydrogen carbonate is not obtained in the solid form while all other elements form solid hydrogen carbonates. 

» Lithium unlike other alkali metal forms no ethynide on reaction with ethyne.

» Lithium nitrate when heated it gives lithium oxide, Li 2 O, whereas other alkali metal nitrates decompose to form the corresponding nitrite. 

      4LiNO3 →2 Li 2 O + 4 NO 2 + O2 

» Li F and Li 2 O are comparatively much less soluble in water than the corresponding compounds of other alkali metals. 

» Lithium hydroxide is less basic than the other hydroxides in the group and therefore, many of its salts are less stable, Li2CO3 , LiNO3 and LiOH all form the oxides on little heating; the analogous compounds of the rest of the group are stable. Another example of its less basic nature is that though lithium forms a bicarbonates in solution, it does not form a solid bicarbonate, where as the other all form stable solid carbonates. 

» Lithium reacts directly with carbon to form anionic carbide. No other group 1 elements do this, but group 2 elements all react similarly with carbon. 

»  Lithium has a great tendency to form complexes than have the heavier elements, and ammoniated salts such as [Li(NH 3)4] + exist as solids.