Lithium (Li)

Lithium is a soft, shiny, silver-white alkali metal and the lightest of the solid elements. It can be found in minerals, such as petalite and spodumene, mineral springs and brine deposits. The nucleus of its most common isotope consists of three protons and four neutrons.

Although it is harder than the other alkali metals, lithium is softer than lead and can be rolled into sheets or pulled into wire. Lithium will float on water before reacting with it to form lithium hydroxide and hydrogen. The reaction with water is so great that lithium is usually stored in mineral oil to avoid a reaction with the moisture in the air.

Essential Facts

Atomic number 3
Name Lithium
Symbol Li
Atomic mass 6.941
Classification Alkali Metal
State at 20°C Solid
Melting point 180.5°C
Boiling point 1342°C

History

Johan Arfwedson discovered lithium in the mineral petalite in 1817. The two other alkali metals that had been discovered before lithium, sodium and potassium, were from vegetable sources.

The distinction between the mineral and vegetable sources was reflected in lithium’s name. In 1818 the name lithium was coined by combining líthos (Greek for stone) with the New Latin suffix -ium.

Isotopes

Lithium has two stable isotopes, lithium-6 and lithium-7, with lithium-7 forming 92.5% of the mix. When bombarded with neutrons, lithium-6 reacts to produce helium and the hydrogen-3 isotope, tritium. In contrast, lithium-7 is a poor absorber of neutrons and so can be used as a coolant in nuclear reactors.

Nuclear bombardment has also produced two unstable isotopes of lithium, but not for long. Both isotopes have short half-lives. The half-lives of lithium-8 and lithium-9 are 0.855 second and 0.17 second respectively.

Production

The extraction of lithium metal from the various mineral ores is a multistage process. Firstly, lithium carbonate can be extracted from the ore by a variety of means. Next, the lithium carbonate is treated with hydrochloric acid, resulting in the production of lithium chloride.

A mixture of lithium chloride and potassium chloride is then prepared and electrolysed. The mixture has a lower melting point than lithium chloride so the electrolysis requires a lower temperature. As lithium chloride decomposes at a lower voltage than potassium chloride, lithium is produced at the cathode with a purity of around 97%.

Purity can be increased by remelting the lithium and removing the potassium and other impurities that either sink to the bottom or float to the top. The largest supplier of lithium and its compounds is currently Chile.

Uses

Lithium has a variety of uses. Lithium is present in the anode of many rechargeable an non rechargeable batteries used in household electrical items. Lithium compounds are also used in the production of synthetic rubber.

As a scavenger, lithium is used in the refining of several metals and non metals, including nickel and sulphur, because it is reacts easily. Lithium alloys have many uses in the aerospace industry. Adding a small quantity of lithium to aluminium produces a much harder alloy and lithium-magnesium alloy is a lightweight material.

Despite the failure of lithium salts in the treatment of gout in the 19th century, lithium does have a major medical use. Lithium carbonate is used successfully in the treatment of bipolar disorder (or manic depression).

Previous Element

Helium (He)

Next Element

Beryllium (Be)

Related Elements

Hydrogen (H), Helium (He), Carbon (C), Oxygen (O), Sodium (Na), Magnesium (Mg), Aluminium / Aluminum (Al), Sulphur / Sulfur (S), Chlorine (Cl), Potassium (K), Nickel (Ni), Lead (Pb)

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