Lithium

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3 helium ← lithium → beryllium H ↑ Li ↓ Na Periodic table - Extended periodic table
General
Name, symbol, number	lithium, Li, 3
Chemical series	alkali metals
Group, period, block	1, 2, s
Appearance	silvery white/grey
Standard atomic weight	6.941(2) g·mol−1
Electron configuration	1s2 2s1
Electrons per shell	2, 1
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, 2448 °F)
Critical point	(extrapolated) 3223 K, 67 MPa
Heat of fusion	3.00 kJ·mol−1
Heat of vaporization	147.1 kJ·mol−1
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
Crystal structure	cubic body centered
Oxidation states	1 (strongly basic oxide)
Electronegativity	0.98 (Pauling scale)
Ionization energies	1st: 520.2 kJ/mol
	2nd: 7298.1 kJ/mol
	3rd: 11815.0 kJ/mol
Atomic radius	145 pm
Atomic radius (calc.)	167 pm
Covalent radius	134 pm
Van der Waals radius	182 pm
Miscellaneous
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
Selected isotopes
Main article: Isotopes of lithium iso NA half-life DM DE (MeV) DP 6Li 7.5% Li is stable with 3 neutrons 7Li 92.5% Li 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 (IPA: [ˈlɪθiəm]) (from Greek λιθoς (lithos), "stone") is a chemical element with the symbol Li and atomic number 3. 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.

Lithium (mostly ⁷Li) was one of the few elements synthesized in the Big Bang, although its quantity has vastly decreased. The reasons for its disappearance and the processes by which new lithium is created continue to be important matters of study in astronomy. Lithium is the 33rd most abundant element on Earth,^[1] but due to its high reactivity only appears there 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 it 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 nuclear reaction, and lithium deuteride serves as the fusion fuel in staged thermonuclear weapons.

Contents 1 Characteristics 1.1 Physical 1.2 Chemical 2 Occurrence 3 Production 4 Isotopes 5 History 6 Applications 6.1 Medical Use 6.2 Other uses 7 Regulation 8 Precautions 9 See also 10 References 11 External links

[edit] Characteristics

Like other alkali metals, lithium has a single valence electron which it will readily lose to form a cation, indicated by the element's low electronegativity. As a result, lithium is easily deformed, highly reactive, and has lower melting and boiling points than most metals. However, these and many other properties attributable to alkali metals' weakly-held valence electron are most diminished in lithium, as it possesses the smallest atomic radius and thus the highest electronegativity. In addition, 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 in N₂, the formation of an oxide when burnt in O₂, salts with similar solubilities, and thermally-instable carbonates and nitrides.^[2]

[edit] Physical

Lithium is soft enough to be cut with a knife, though this is more difficult than cutting sodium. The fresh metal has a silvery-white color which only remains untarnished in dry air.^[2] Lithium has about half the density of water, giving solid sticks of lithium metal the odd heft of a light-to-medium wood like pine. The metal floats highly in hydrocarbons; in the laboratory, jars of lithium are typically composed of black-coated sticks held down in hydrocarbon mechanically by the jar's lid and other sticks.

Lithium is greatly heat-resistant, possessing a low coefficient of thermal expansion and the lowest specific heat capacity of any solid element. Lithium has also been found to be superconductive below 400 μK. This finding paves the way for further study of superconductivity, as lithium's atomic lattice is the simplest of all metals.

[edit] Chemical

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).^[2]

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 when exposed to water and water vapours in oxygen. It is the only metal that reacts with nitrogen at room temperature.

Lithium metal is flammable and potentially explosive when exposed to air and especially water, though it is far less dangerous than other alkali metals in this regard. The lithium-water reaction at normal temperatures is brisk but not violent. Lithium fires are difficult to extinguish, requiring special chemicals designed to smother them.

[edit] Occurrence

On Earth, lithium is widely distributed, but because of its reactivity does not occur in its free form. In keeping with the origin of its name, lithium forms a minor part of almost all igneous rocks and is also found in many natural brines. Lithium is the 33rd most abundant element, contained particularly in the minerals spodumene, lepidolite, petalite, and amblygonite. On average, Earth's crust contains 65 ppm (.0007%) lithium.^[1]

In humans lithium compounds have not been found to play a natural biological role; large amounts are slightly toxic. Lithium appears to be an essential trace element for goats, and possibly rats, suggesting a role in humans by analogy. However, the essentiality of ultratrace mineral in humans is far more difficult to determine, due to the difficulty and ethical issues involved with the experiments, which involve total isolation from the environment, and unpalatable semi-synthetic foods.

[edit] Production

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

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).^[3]

Chile is currently the leading lithium metal producer in the world, with Argentina next. Both countries recover the lithium from brine pools. In the United States lithium is similarly recovered from brine pools in Nevada.^[4]

China may emerge as a significant producer of brine-based lithium carbonate towards the end of this decade. Potential capacity of up to 45,000 tonnes per year could come on-stream if projects in Qinghai province and Tibet proceed.^[5]

See also Lithium minerals.

[edit] Isotopes

Main article: Isotopes of lithium

Naturally occurring lithium is composed of two stable isotopes ⁶Li and ⁷Li, the latter being the more abundant (92.5% natural abundance). 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 ⁶Li is also produced in stars). Lithium isotopes fractionate substantially during a wide variety of natural processes, including mineral formation (chemical precipitation), metabolism, and ion exchange. Lithium ion substitutes 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.

[edit] History

Petalite, which has lithium in it, was discovered by the Brazilian scientist José Bonifácio de Andrade e Silva in the late 1700s on a trip to Sweden. Lithium was discovered by Johan August Arfwedson in 1817. Arfwedson found the new element within the minerals spodumene and lepidolite in a petalite ore (LiAl(Si₂O₅)₂) that he was analyzing during a routine investigation of some minerals from a mine on the island Utö in Sweden. In 1818 Christian Gmelin was the first to observe that lithium salts give a bright red color in flame. Both men tried and failed to isolate the element from its salts.

The element was not isolated until William Thomas Brande and Sir Humphry Davy later used electrolysis on lithium oxide in 1818. Robert Bunsen and Matiessen isolated larger quantities of the metal by electrolysis of lithium chloride in 1855. Commercial production of lithium metal was achieved in 1923 by the German company Metallgesellschaft through using electrolysis of molten lithium chloride and potassium chloride. It was apparently given the name "lithium" (Greek λιθoς (lithos), meaning "stone") because it was discovered from a mineral while other common alkali metals were first discovered from plant tissue.

[edit] Applications

Because of its specific heat capacity, the highest of all solids, lithium is often used in heat transfer applications.

It is an important ingredient in cathode materials, used in rechargeable and single-use batteries because of its high electrochemical potential, light weight, and high current density.

Large quantities of lithium are also used in the manufacture of organolithium reagents, especially n-butyllithium which has many uses in fine chemical and polymer synthesis.

[edit] Medical Use

Main article: Lithium pharmacology

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. It is also sometimes prescribed as a preventive treatment for migraine disease and cluster headaches.

The active principle in these salts is the lithium ion Li⁺, which interacts with the normal function of sodium ions to produce numerous changes in the neurotransmitter activity of the brain. Therapeutically useful amounts of lithium are only slightly lower than toxic amounts, so the blood levels of lithium must be carefully monitored during treatment.

Common side effects include muscle tremors, twitching, ataxia, nephrogenic diabetes insipidus (polyuria and polydipsia) and seizures. Most of the side-effects are a result caused by the increased elimination of potassium.

[edit] Other uses

• Lithium chloride and lithium bromide are extremely hygroscopic and frequently used as desiccants.
• Lithium stearate is a common all-purpose high-temperature lubricant.
• Lithium is an alloying agent used to synthesize organic compounds.
• 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.
• Lithium is sometimes used in glasses and ceramics including the glass for the 200-inch (5.08 m) telescope at Mt. Palomar.
• Alloys of the metal with aluminium, cadmium, copper, and manganese are used to make high performance aircraft parts.
• 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 per cent of mobile phones.^[6]
• The high non-linearity of lithium niobate also makes a good choice for non-linear optics 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 apparently no longer plays a role in modern nuclear weapons, having been replaced entirely for the purpose by elemental tritium, which is lighter and easier to handle than lithium salts. ^{[citation needed]}
• Metallic Lithium and its complex hydrides such as e.g. Li[AlH₄] are considered as high energy additives to rocket propellants^[3].
• Lithium peroxide, Lithium nitrate, Lithium chlorate and Lithium perchlorate are used and thought of as oxidizers in both rocket propellants and oxygen candles to supply submarines and space capsules with oxygen.^[7]
• 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 + ³T. 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.
• 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 metal is used as a reducing agent in some types of methamphetamine production, particularly in illegal amateur “meth labs.”
• Lithium hydroxide is an efficient and lightweight purifier of air. In confined areas, such as aboard spacecraft and submarines, the concentration of carbon dioxide can approach unhealthy or toxic levels. Lithium hydroxide absorbs the carbon dioxide from the air by reacting with it to form lithium carbonate. Any alkali hydroxide will absorb CO₂, but lithium hydroxide is preferred, especially in spacecraft applications, because of the low formula weight conferred by the lithium. Even better materials for this purpose include lithium peroxide (Li₂O₂) that, 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.

[edit] 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. However, the effectiveness of such restrictions in controlling illegal production of methamphetamine remains indeterminate and controversial.

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. However, most consumer lithium batteries have thermal overload protection built-in to prevent this type of incident, or their design inherently limits short-circuit currents.

Lithium is a component for thermonuclear weapons (so called "hydrogen bombs") and applications of lithium for this purpose in the nuclear weapons industry is pursued in developing nuclear powers like India, and presumably others.

[edit] Precautions

Lithium metal, due to its alkaline tarnish, is corrosive and requires special handling to avoid skin contact. Breathing lithium dust or lithium compounds (which are often alkaline) can irritate the nose and throat; higher exposure to lithium can cause a build-up of fluid in the lungs, leading to pulmonary edema. The metal itself is usually less a handling hazard than the caustic hydroxide produced when it is in contact with moisture. Lithium should be stored in a non-reactive compound such as naphtha or a hydrocarbon.