lithium

helium ← lithium → beryllium H ↑ Li ↓ Na 3Li Periodic table
Appearance
silvery white (seen here in oil)
General
Name, symbol, number	lithium, Li, 3
Element category	alkali metal
Group, period, block	1, 2, s
Standard atomic weight	6.941(2) g·mol−1
Electron configuration	1s2 2s1
Electrons per shell	2, 1 (Image)
Physical properties
Phase	solid
Density (near r.t.)	0.534 g·cm−3
Liquid density at m.p.	0.512 g·cm−3
Melting point	453.69 K (180.54 °C, 356.97 °F)
Boiling point	1615 K (1342 °C, 2456.6 °F)
Critical point	(extrapolated) 3223 K, 67 MPa
Heat of fusion	3.00 kJ·mol−1
Heat of vaporization	147.1 kJ·mol−1
Specific heat capacity	(25 °C) 24.860 J·mol−1·K−1
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K 797 885 995 1144 1337 1610
Atomic properties
Oxidation states	+1, -1 (strongly basic oxide)
Electronegativity	0.98 (Pauling scale)
Ionization energies	1st: 520.2 kJ·mol−1
	2nd: 7298.1 kJ·mol−1
	3rd: 11815.0 kJ·mol−1
Atomic radius	152 pm
Covalent radius	128±7 pm
Van der Waals radius	182 pm
Miscellaneous
Crystal structure	body-centered cubic
Magnetic ordering	paramagnetic
Electrical resistivity	(20 °C) 92.8 nΩ·m
Thermal conductivity	(300 K) 84.8 W·m−1·K−1
Thermal expansion	(25 °C) 46 µm·m−1·K−1
Speed of sound (thin rod)	(20 °C) 6000 m/s
Young's modulus	4.9 GPa
Shear modulus	4.2 GPa
Bulk modulus	11 GPa
Mohs hardness	0.6
CAS registry number	7439-93-2
Most stable isotopes
Main article: Isotopes of lithium iso NA half-life DM DE (MeV) DP 6Li 7.5% 6Li is stable with 3 neutrons 7Li 92.5% 7Li is stable with 4 neutrons 6Li content may be as low as 3.75% in natural samples. 7Li would therefore have a content of up to 96.25%.
References
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Lithium ingots with a thin layer of black oxide tarnish

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.^[1] 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 few elements synthesized in the Big Bang; its abundance is now vastly less than that predicted by theory^[2]; the processes by which new lithium is created and destroyed, and the true value of its abundance,^[3] continue to be active matters of study in astronomy.^[4][5][6] 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 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 vital biological function in humans, though the neurological effect of the lithium ion Li⁺ makes some lithium salts useful as a mood stabilizing drug. Lithium and its compounds have several industrial 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 a 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 was later 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.^[7][8][9] The element was not isolated until 1821, when William Thomas Brande performed electrolysis on lithium oxide, a process previously employed by Sir Humphry Davy to isolate potassium and sodium.^[8][10] 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.^[7][11]

Properties

Lithium pellets (covered in white lithium hydroxide)

Like other alkali metals, lithium has a single weakly held valence electron which it will readily lose to form a cation. As a result lithium is easily deformed, highly reactive, and has a low melting and boiling point. The properties and chemistry of Lithium are modified further due to its small atomic radius or ionic radius. Lithium is the least electropositive of the alkali group.

Lithium is soft enough to be cut with a knife with some difficulty; it is the hardest of the alkali metals. The fresh metal has a silvery-white color which remains untarnished only in dry air.^[12] Lithium has about half the density of water, similar to pine wood, and lithium sticks have a heft similar to wooden dowels. Lithium floats in hydrocarbons, so laboratory stock lithium sticks are typically held under the protective liquid by the container lid.

Lithium possesses a low coefficient of thermal expansion and the highest specific heat capacity of any solid element. Lithium is superconductive below 400 μK at standard pressure^[13] and at higher temperatures (more than 9 Kelvin) at very high pressures (over 200,000 atmospheres)^[14]

At cryogenic temperatures, lithium, like sodium, undergoes diffusionless phase change transformations. At 4.2K it has a Rhombohedral (with a nine-layer repeat spacing)^[15], at higher temperatures it transforms to Face-centered cubic and then Body-centered cubic. At liquid-helium temperatures (4 K) the rhombohedral structure is the most prevalent.

Chemistry

In moist air, lithium metal rapidly tarnishes to form a black coating of lithium hydroxide (LiOH and LiOH·H₂O), lithium nitride (Li₃N) and lithium carbonate (Li₂CO₃, the result of a secondary reaction between LiOH and CO₂).^[12]

When placed over a flame lithium gives off a striking crimson color, but when it burns strongly the flame becomes a brilliant white. Lithium will ignite and burn in oxygen when exposed to water or water vapours. It is the only metal that reacts with nitrogen at room temperature.^{[clarification needed]}

Lithium metal is flammable and potentially explosive when exposed to air and especially water, though less so than other alkali metals. The lithium-water reaction at normal temperatures is brisk but not violent, though the hydrogen produced can ignite. Like all alkali metals, lithium fires are difficult to extinguish, requiring dry powder fire extinguishers, specifically Class D type (see Types of extinguishing agents).

Lithium compounds

This section requires expansion.

Lithium has a diagonal relationship with magnesium, an element of similar atomic and ionic radius. Chemical resemblances between the two metals include the formation of a nitride by reaction with N₂, the formation of an oxide when burnt in O₂, salts with similar solubilities, and thermal instability of the carbonates and nitrides.^[12]

Isotopes

Naturally occurring lithium is composed of two stable isotopes, ⁶Li and ⁷Li, the latter being the more abundant (92.5 percent natural abundance).^[16] Both natural isotopes have anomalously low nuclear binding energy per nucleon compared to the next lighter and heavier elements, Helium and Beryllium, which means that alone among stable light elements, Lithium can produce net energy through nuclear fission. Seven radioisotopes have been characterized, the most stable being ⁸Li with a half-life of 838 ms and ⁹Li with a half-life of 178.3 ms. All of the remaining radioactive isotopes have half-lives that are shorter than 8.6 ms. The shortest-lived isotope of lithium is ⁴Li, which decays through proton emission and has a half-life of 7.58043x10^-23 s.

⁷Li is one of the primordial elements (or, more properly, primordial isotopes) produced in Big Bang nucleosynthesis. A small amount of both ⁶Li and ⁷Li are produced in stars, but are thought to be burned as fast as it is produced.^[17] Lithium isotopes fractionate substantially during a wide variety of natural processes, including mineral formation (chemical precipitation), metabolism, and ion exchange. Lithium ions substitute for magnesium and iron in octahedral sites in clay minerals, where ⁶Li is preferred to ⁷Li, resulting in enrichment of the light isotope in processes of hyperfiltration and rock alteration. The exotic ¹¹Li is known to exhibit a nuclear halo.

Natural occurrence

Lithium is about as common as chlorine in the Earth's upper continental crust, on a per-atom basis.

According to theory, the stable isotopes lithium-6 and lithium-7 were created in the Big Bang, but the amounts are unclear. There is general agreement that they were larger than the cosmos contains today. Because of the method by which elements are built up by fusion in stars, there is a general trend in the cosmos that the lighter elements are more common. However, lithium (element number 3) is tied with krypton as the 32nd/33rd most abundant element in the cosmos (see Cosmochemical Periodic Table of the Elements in the Solar System), being less common than any element before scandium (element 21). It is not until atomic number 36 (krypton) and beyond that chemical elements are found to be universally less common in the cosmos than lithium. The reasons have to do with the failure of any good mechanisms to synthesize lithium in the fusion reactions between nuclides in supernovae. Due to the absence of any quasi-stable nuclide with five nucleons, nuclei of lithium-5 produced from helium and a proton has no time to fuse with a second proton or neutron to form a six nucleon isotope which might decay to lithium-6, even under extreme conditions of bombardment. Also, the product of helium-helium fusion (berylium-8) is immediately unstable toward disintegration to helium again, and is thus not available for formation of lithium. Some lithium-7 is formed in the pp III branch of the proton-proton chain in main sequence and red giant stars, but it is normally consumed by lithium burning as fast as it is formed. This leaves new formation of the stable isotopes lithium 6 and 7 to rare cosmic ray spallation on carbon or other elements in cosmic dust. Meanwhile, existing Li-6 and Li-7 is destroyed in many nuclear reactions in supernovae and by lithium burning in main sequence stars, resulting in net removal of lithium from the cosmos.

Lithium is widely distributed on Earth^[18] but does not naturally occur in elemental form due to its high reactivity. Estimates for crustal content range from 20 to 70 ppm by weight.^[12] In keeping with its name, lithium forms a minor part of igneous rocks, with the largest concentrations in granites. Granitic pegmatites also provide the greatest abundance of lithium-containing minerals, with spodumene and petalite being the most commercially viable sources.^[12] A newer source for lithium is hectorite clay, the only active development of which is through Western Lithium Corp. in the USA. ^[19]

According to the Handbook of Lithium and Natural Calcium, "Lithium is a comparatively rare element, although it is found in many rocks and some brines, but always in very low concentrations. There are a fairly large number of both lithium mineral and brine deposits but only comparatively a few of them are of actual or potential commercial value. Many are very small, others are too low in grade."^[20] The most important deposit of lithium is in the Salar de Uyuni area of Bolivia, which holds half of the world's known reserves. According to the US Geological Survey the reserves of lithium in Bolivia are estimated at 5.4 million tons, compared with 3 million tons in Chile, 1.1 million tons in China and just 410,000 tons in the United States.^[21][22] Worldwide lithium reserves are estimated at 30 million tonnes in 2015.^[23]

Seawater contains an estimated 230 billion tons of lithium, though at a low concentration of 0.1 to 0.2 ppm.^[24]

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, compared with 1.5 volts for lead/acid or zinc cells. Because of its low atomic mass, it also has 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^[25] in anionic polymerisation of unfunctionalised olefins.^[26][27][28]

Medical use

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 antidepressants. 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.^[29]

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). Serotonin is related to mood stability. 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^[30] and hypothyroidism. Long term use is linked to hyperparathyroidism^[31], hypercalcemia (bone loss), hypertension, kidney damage, nephrogenic diabetes insipidus (polyuria and polydipsia), seizures^[32] and weight gain.^[33] Some of the side-effects are a result of the increased elimination of potassium.

There appears to be an increased risk of Ebstein (cardiac) Anomaly in infants born to women taking lithium during the first trimester of pregnancy.

According to a study in 2009 at Oita University in Japan and published in the British Journal of Psychiatry, communities whose water contained larger amounts of lithium had significantly lower suicide rates^{[34][35][36][37]} but did not address whether lithium in drinking water causes the negative side effects associated with higher doses of the element.^[38]

Other uses

The red lithium flame leads to Lithium's use in flares and pyrotechnics

• Electrical and electronic uses:
  • Lithium batteries are disposable (primary) batteries with 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 applications are used in more than 60 percent of mobile phones.^[39]
• 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.
  • When used as a flux for welding or soldering, lithium promotes the fusing of metals during and eliminates the forming of oxides by absorbing impurities. Its 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 focal lenses, including spectacles and the glass for the 200-inch (5.08 m) telescope at Mt. Palomar.^{[citation needed]}
  • The high non-linearity of lithium niobate also makes it useful in 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 a Li[AlH₄], are used as high energy additives to rocket propellants^[3].
  • Lithium peroxide, lithium nitrate, lithium chlorate and lithium perchlorate are used as oxidizers in rocket propellants, and also in oxygen candles that supply submarines and space capsules with oxygen.^[40]
• 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]}
  • In conceptualized nuclear fusion power plants, Lithium will be used to produce tritium in magnetically confined 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 is used 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 carbon dioxide from the air by reacting with it to form lithium carbonate, and is preferred over other alkaline hydroxides for its low weight. Lithium peroxide (Li₂O₂) in presence of moisture not only absorbs carbon dioxide to form lithium carbonate, but also releases oxygen. E.g. 2 Li₂O₂ + 2 CO₂ → 2 Li₂CO₃ + O₂.
  • Lithium compounds are used in 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. The reaction generates enormous heat which is used to generate steam from seawater. The steam propels the torpedo in a closed Rankine cycle.^[41]

Production and world supply

Lithium mine, Salar del Hombre Muerto, Argentina. The brine in this salar is rich in lithium, and the mine concentrates the brine by pumping it into solar evaporation ponds. 2009 image from NASA’s EO-1 satellite.

Since the end of World War II lithium metal production has greatly increased. The metal is separated from other elements in igneous minerals such as those above. Lithium salts are extracted from the water of mineral springs, brine pools and brine deposits.

The metal is produced electrolytically from a mixture of fused lithium and potassium chloride. In 1998 it was about US$ 43 per pound ($95 per kg).^[42]

Deposits of lithium are found in South America throughout the Andes mountain chain. Chile is the leading lithium metal producer, followed by Argentina. Both countries recover the lithium from brine pools. In the United States lithium is recovered from brine pools in Nevada.^[43]

Nearly half the world's known reserves are located in Bolivia, a nation sitting along the central eastern slope of the Andes. In 2009 Bolivia is negotiating with Japanese and French firms to begin extraction.^[44] According to the US Geological Survey, Bolivia's Uyuni Desert has 5.4 million tons of lithium, which can be used to make batteries for hybrid and electric vehicles.^[44] This is the largest amount of lithium in any country, compared to Chile's 3 million tons and the United States's 760,000 tons.^[44][45]

China may emerge as a significant producer of brine-source lithium carbonate around 2010. There is potential production of up to 55,000 tons per year if projects in Qinghai province and Tibet proceed.^[46]

The total amount of lithium recoverable from global reserves has been estimated at 35 million tonnes, which includes 15 million tons of the known global lithium reserve base.^[47]

In 1976 a National Research Council Panel estimated lithium resources at 10.6 million tons for the Western World.^[48] With the inclusion of Russian and Chinese resources as well as new discoveries in Australia, Serbia, Argentina and the United States, the total had nearly tripled by 2008.^[49][50]

Precautions

Due to its alkaline tarnish, lithium metal is corrosive and requires special handling to avoid skin contact. Breathing lithium dust or lithium compounds (which are often alkaline) initially irritate the nose and throat, while higher exposure can cause a buildup of fluid in the lungs, leading to pulmonary edema. The metal itself is a handling hazard because of the caustic hydroxide produced when it is in contact with moisture. Lithium is safely stored in non-reactive compounds such as naphtha.^[51]

Regulation

Some jurisdictions limit the sale of lithium batteries, which are the most readily available source of lithium metal for ordinary consumers. Lithium can be used to reduce pseudoephedrine and ephedrine to methamphetamine in the Birch reduction method, which employs solutions of alkali metals dissolved in anhydrous ammonia.

Carriage and shipment of some kinds of lithium batteries may be prohibited aboard certain types of transportation (particularly aircraft) because of the ability of most types of lithium batteries to fully discharge very rapidly when short-circuited, leading to overheating and possible explosion in a process called thermal runaway. Most consumer lithium batteries have thermal overload protection built-in to prevent this type of incident, or their design inherently limits short-circuit currents. Internal shorts have been known to develop due to manufacturing defects or damage to batteries that can lead to spontaneous thermal runaway.^[52]

See also

• Lithium compounds
• Lithium-based grease
• Dilithium

References

External links

Look up lithium in Wiktionary, the free dictionary.

Wikimedia Commons has media related to: Lithium

• USGS: Lithium Statistics and Information
• WebElements.com – Lithium
• It's Elemental – Lithium
• University of Southampton, Mountbatten Centre for International Studies, Nuclear History Working Paper No5.