|Name: lithium||Group number: 1|
|Symbol: Li||Group name: Alkali metal|
|Atomic number: 3||Period number: 2|
|Atomic weight: [ 6.941 (2)] g m r||Block: s-block|
|CAS Registry ID: 7439-93-2||Voice: |
|Standard state: solid at 298 K||Colour: silvery white/grey|
|Classification: Metallic||Availability: |
Lithium is a Group 1 (IA) element containing just a single valence electron (1s22s1). 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.
Nearing Zero cartoon included by kind permission of Nick Kim.
IsolationHere is a brief summary of the isolation of lithium.
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 a form is first converted into the softer b 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 sould be expensive to melt it in order to carry out the electrolysis. However a mixture of LiCl (55%) and KCl (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-