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Lithium (pronounced /ˈlɪθiəm/) is the chemical element with atomic number 3, and is represented by the symbol Li. It is a soft alkali metal with a silver-white color. Under standard conditions, it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly reactive, corroding quickly in moist air to form a black tarnish. For this reason, lithium metal is typically stored under the cover of oil. When cut open, lithium exhibits a metallic lustre, but contact with oxygen quickly turns it back to a dull silvery grey color. Lithium is highly flammable.

According to theory, lithium was one of the very few elements synthesized in the Big Bang; its abundance is now vastly less than that predicted by theory; the processes by which new lithium is created and destroyed, and the true value of its abundance continue to be active matters of study in astronomy. Though very light in atomic weight lithium is less common in the universe than any of the first 20 elements due to its low nuclear binding energy.

Due to its high reactivity it only appears naturally on Earth in the form of compounds. Lithium occurs in a number of pegmatitic minerals, but is also commonly obtained from brines and clays; on a commercial scale, lithium metal is isolated electrolytically from a mixture of lithium chloride and potassium chloride.

Trace amounts of lithium are present in the oceans and in some organisms, though the element serves no apparent biological function in humans. Nevertheless, the neurological effect of the lithium ion Li+ makes some lithium salts useful as a class of mood stabilizing drugs. Lithium and its compounds have several other commercial applications, including heat-resistant glass and ceramics, high strength-to-weight alloys used in aircraft, and lithium batteries. Lithium also has important links to nuclear physics: the splitting of lithium atoms was the first man-made form of a nuclear reaction, and lithium deuteride serves as the fusion fuel in staged thermonuclear weapons.

History and etymology
Petalite (lithium aluminium silicate) was first discovered in 1800 by the Luso-Brazilian scientist José Bonifácio de Andrade e Silva, who discovered the mineral in a Swedish iron mine on the island of Utö. However, it was not until 1817 that Johan August Arfwedson, then a trainee in the laboratory of Jöns Jakob Berzelius, discovered the presence of a new element while analyzing petalite ore. The element formed compounds similar to those of sodium and potassium, though its carbonate and hydroxide were less water soluble and had a larger capacity to neutralize acid. Berzelius gave the alkaline material the name "lithos", from the Greek λιθoς (lithos, "stone"), to reflect its discovery in a mineral, as opposed to sodium and potassium which had been discovered in plant tissue; its name would later be standardized as "lithium". Arfwedson later showed that this same element was present in the mineral ores spodumene and lepidolite. In 1818, Christian Gmelin was the first to observe that lithium salts give a bright red color in flame. However, both Arfwedson and Gmelin tried and failed to isolate the element from its salts. The element was not isolated until 1821, when William Thomas Brande performed electrolysis on lithium oxide, a process which had previously been employed by Sir Humphry Davy to isolate potassium and sodium. Brande also described pure salts of lithium, such as the chloride, and performed an estimate of its atomic weight. In 1855, Robert Bunsen and Augustus Matthiessen produced large quantities of the metal by electrolysis of lithium chloride. Commercial production of lithium metal began in 1923 by the German company Metallgesellschaft AG through the electrolysis of a molten mixture of lithium chloride and potassium chloride
Major applications of the metal
Because of its specific heat capacity, the highest of all solids, lithium is often used in heat transfer applications.

In the latter years of the 20th century lithium became important as an anode material; used in lithium-ion batteries because of its high electrochemical potential, a typical cell can generate approximately 3 volts (compare with 1.5 volts for lead/acid or zinc cells); additionally its low atomic mass gives a high charge (and power) to weight ratio.

Lithium is also used in the pharmaceutical and fine chemical industry in the manufacture of organolithium reagents which are used both as strong bases and as reagents for the formation of carbon carbon bonds. Organolithiums are also used in polymer synthesis, as catalysts/initiators in anionic polymerisation of unfunctionalised olefins

Medical use
Main article: Lithium pharmacology
Lithium salts were used during the 19th century to treat gout. Lithium salts such as lithium carbonate (Li2CO3), lithium citrate, and lithium orotate are mood stabilizers. They are used in the treatment of bipolar disorder, since unlike most other mood altering drugs, they counteract both mania and depression. Lithium can also be used to augment other antidepressant drugs. Because of Lithium's nephrogenic diabetes insipidus effects, it can be used to help treat the syndrome of inappropriate diuretic hormone (SIADH). It was also sometimes prescribed as a preventive treatment for migraine disease and cluster headaches.

The active principle in these salts is the lithium ion Li+. Although this ion has a smaller diameter than either Na+ or K+, in a watery environment like the cytoplasmic fluid, Li+ binds to the hydrogen atoms of water making it effectively larger than either Na+ or K+ ions. How Li+ works in the CNS is still a matter of debate. Li+ elevates brain levels of tryptophan, 5-HT (serotonin), and 5-HIAA (a serotonin metabolite). The serotonin system is related to stability of mood. Li+ also reduces catecholamine activity in the brain (associated with brain activation and mania), by enhancing reuptake and reducing release. Therapeutically useful amounts of lithium (~ 0.6 to 1.2 mmol/l) are only slightly lower than toxic amounts (>1.5 mmol/l), so the blood levels of lithium must be carefully monitored during treatment to avoid toxicity.

Common side effects of lithium treatment include muscle tremors, twitching, ataxia and hypothyroidism. Long term use is linked to hyperparathyroidism, hypercalcemia (bone loss), hypertension, kidney damage, nephrogenic diabetes insipidus (polyuria and polydipsia) and seizures Some of the side-effects are a result of the increased elimination of potassium.

Pregnancy - teratogenic properties: Ebstein (cardiac) Anomaly - There appears to be an increased risk of this abnormality in infants of women taking lithium during the first trimester of pregnancy.

A study in 2009 at Oita University in Japan published in the British Journal of Psychiatry communities whose water contained larger amounts of lithium, had significantly lower suicide rates.However, health care professionals have recommended further research to ensure that lithium in drinking water does not result in the negative side effects associated with higher doses of the element.

Other uses
The red lithium flame leads to Lithium's use in flares and pyrotechnicsElectrical and electronic uses:
Lithium batteries are disposable (primary) batteries that have lithium metal or lithium compounds as an anode. Lithium batteries are not to be confused with lithium-ion batteries which are high energy-density rechargeable batteries.
Lithium niobate is used extensively in telecommunication products, such as mobile phones and optical modulators, for such components as resonant crystals. Lithium products are currently used in more than 60 percent of mobile phones.
Chemical uses:
Lithium chloride and lithium bromide are extremely hygroscopic and are used as desiccants.
Lithium metal is used in the preparation of organo-lithium compounds.
General engineering:
Lithium stearate is a common all-purpose high-temperature lubricant.
Lithium is used as a flux to promote the fusing of metals during welding and soldering. It also eliminates the forming of oxides during welding by absorbing impurities. This fusing quality is also important as a flux for producing ceramics, enamels, and glass.
Alloys of the metal with aluminium, cadmium, copper and manganese are used to make high performance aircraft parts. See also Lithium-aluminium alloys
Optics:
Lithium is sometimes used in glasses and ceramics including the glass for the 200-inch (5.08 m) telescope at Mt. Palomar.[citation needed]
The high non-linearity of lithium niobate also makes a good choice for non-linear optics applications. Lithium fluoride artificially grown as crystal is clear and transparent and often used in specialist optics for IR, UV and VUV (vacuum UV) applications. It has the lowest refractive index and the farthest transmission range in the deep UV of all common materials.
Rocketry:
Metallic lithium and its complex hydrides such as e.g. Li[AlH4] are considered as high energy additives to rocket propellants].
Lithium peroxide, lithium nitrate, lithium chlorate, and lithium perchlorate are used as oxidizers in both rocket propellants and oxygen candles to supply submarines and space capsules with oxygen.
Nuclear applications:
Lithium deuteride was the fusion fuel of choice in early versions of the hydrogen bomb. When bombarded by neutrons, both 6Li and 7Li produce tritium—this reaction, which was not fully understood when hydrogen bombs were first tested, was responsible for the runaway yield of the Castle Bravo nuclear test. Tritium fuses with deuterium in a fusion reaction that is relatively easy to achieve. Although details remain secret, lithium-6 deuteride still apparently plays a role in modern nuclear weapons, as a fusion material.
Lithium fluoride (highly enriched in the common isotope lithium-7) forms the basic constituent of the preferred fluoride salt mixture (LiF-BeF2) used in liquid-fluoride nuclear reactors. Lithium fluoride is exceptionally chemically stable and LiF/BeF2 mixtures have low melting points and the best neutronic properties of fluoride salt combinations appropriate for reactor use.[clarification needed]
Lithium will be used to produce tritium in magnetically confined nuclear fusion reactors using deuterium and tritium as the fuel. Tritium does not occur naturally and will be produced by surrounding the reacting plasma with a 'blanket' containing lithium where neutrons from the deuterium-tritium reaction in the plasma will react with the lithium to produce more tritium. 6Li + n → 4He + 3H. Various means of doing this will be tested at the ITER reactor being built at Cadarache, France.
Lithium is used as a source for alpha particles, or helium nuclei. When 7Li is bombarded by accelerated protons, 8Be is formed, which undergoes spontaneous fission to form two alpha particles. This was the first man-made nuclear reaction, produced by Cockroft and Walton in 1929.
Other uses:
Lithium hydroxide (LiOH) is an important compound of lithium obtained from lithium carbonate (Li2CO3). It is a strong base, and when heated with a fat, it produces a lithium soap. Lithium soap has the ability to thicken oils and so is used commercially to manufacture lubricating greases.
Lithium hydroxide and lithium peroxide are used in confined areas, such as aboard spacecraft and submarines for air purification. Lithium hydroxide absorbs the carbon dioxide from the air by reacting with it to form lithium carbonate, being preferred over other alkaline hydroxides for its low weight. Lithium peroxide (Li2O2) in presence of moisture not only absorb carbon dioxide to form lithium carbonate, but also release oxygen. E.g. 2 Li2O2 + 2 CO2 → 2 Li2CO3 + O2.
Lithium compounds can be used to make red fireworks and flares.
The Mark 50 Torpedo Stored Chemical Energy Propulsion System (SCEPS) uses a small tank of sulfur hexafluoride gas which is sprayed over a block of solid lithium, which generates enormous quantities of heat, in turn used to generate steam from seawater. The steam propels the torpedo in a closed Rankine cycle.