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Properties of Lithium
(a) Physical Properties
(i) Lithium is a silvery white metal.
(i) It is the hardest alkali metal but still is soft enough to be cut with a knife.
(ii) Atomic and ionic radii of lithium are the lowest amongst alkali metals.
(b) Chemical Properties
Lithium is highly reactive element. However, among alkali metals lithium is the least reactive.
Alt text: chemical reactions of Lithium
Lithium is the only alkali metal which combines directly with nitrogen to form lithium nitride. Lithium nitride is ionic and is ruby red. On heating it decomposes to its constituent element. It also reacts with water evolving ammonia.
2Li3N → 6Li + N2
Li3N + 3H2O → 3LiOH + NH3
Like other alkali metals, lithium dissolves is liquid ammonia to form a deep blue solution due to formation of ammoniated electrons.
Li + ( X + Y ) NH3 ———→ Li ( NH3)x + e- (NH3)y
However, when NH3 gas is passed over molten lithium. Lithium amide is formed
2Li + 2NH3 —→ 2LiNH2 + H2
Uses of Lithium
(a) Lithium lead alloy (0.05% Li) which is used for making toughened bearings and sheets for cables.
(b) Lithium – Aluminium alloy has great tensile strength and elasticity like that of mild steel. It is used for air craft construction.
(c) Lithium – magnesium alloy (with 14% Li) is extremely tough and corrosion resistant which is used for armour plate and aerospace components.
(d) Lithium is used for refining of metal like copper and nickel as it combines readily with oxygen and nitrogen and thus removes the last traces of oxygen and nitrogen.
(e) Lithium chloride is used in air conditioning plants to regulate the humidity.
(f) Lithium aluminium hydride (LiAlH4) is used as a reducing agent in synthetic organic chemistry
(g) Lithium carbonate is used in making special variety of glass which is very strong and is weather proof.