Lithium

Name:Lithium
Symbol:Li
Atomic Number:3
Atomic Weight:6.941
Density:13.02 g/cm^3
^{Group Number:1
Group Name:Alkali Metals
Standard State:Solid at room temperature
Color:Silvery-white / grey
Classification:Metallic}
Lithium is a Group 1 element containing just a single valence electron.Group 1 elements are called "alkali metals". Lithium is a solid only about half as dense as water. A freshly cut chunk of lithium is silvery, but tarnishes in a minute or so in air to give a grey surface. Lithium is mixed (alloyed) with aluminium and magnesium for light-weight alloys, and is also used in batteries, some greases, some glasses, and in medicine.

Isolation

Lithium would not normally be made in the laboratory as it is so readily available commercially. All syntheses require an electrolytic step as it is so difficult to add an electron to the poorly electronegative lithium ion Li⁺.

The ore spodumene, LiAl(SiO₃)₂, is the most important commercial ore containing lithium. The α form is first converted into the softer β form by heating to around 1100°C. This is mixed carefully with hot sulphuric acid and extracted into water to form lithium sulphate, Li₂SO₄, solution. The sulphate is washed with sodium carbonate, Na₂CO₃, to form a precipitate of the relatively insoluble lithium carbonate, Li₂CO₃.

Li₂SO₄ + Na₂CO₃ → Na₂SO₄ + Li₂CO₃ (solid)

Reaction of lithium carbonate with HCl then provides lithium chloride, LiCl.

Li₂CO₃ + 2HCl → 2LiCl + CO₂ +H₂O

Lithium chloride has a high melting point (> 600°C) meaning that it should be expensive to melt it in order to carry out the electrolysis. However a mixture of Lithium Chloride (55%) and Potassium Chloride (45%) melts at about 430°C and so much less energy and so expense is required for the electrolysis.

cathode: Li⁺(l) + e^- → Li (l)

anode: Cl^-(l) → ¹/₂Cl₂ (g) + e^-