Lithium From Wikipedia, the free encyclopedia This article is about the chemical element. For the use of lithium as a medication, see Lithium (medication). For other uses, see Lithium (disambiguation). This is a good article. Click here for more information. Lithium H ↑ Li ↓ Na helium ← lithium → beryllium Lithium in the periodic table Appearance silvery-white (shown floating in oil) Spectral lines of lithium General properties Name, symbol, number lithium, Li, 3 Pronunciation /ˈlɪθiəm/ li-thee-əm Element category alkali metal Group, period, block 1 (alkali metals), 2, s Standard atomic weight 6.94(1) Electron configuration [He] 2s1 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 453.65 K, 180.50 °C, 356.90 °F Boiling point 1603 K, 1330 °C, 2426 °F Critical point (extrapolated) 3220 K, 67 MPa Heat of fusion 3.00 kJ·mol−1 Heat of vaporization 136 kJ·mol−1 Molar heat capacity 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 (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 Miscellanea Crystal structure body-centered cubic Lithium has a body-centered cubic crystal structure Magnetic ordering paramagnetic Electrical resistivity (20 °C) 92.8 nΩ·m Thermal conductivity 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−1 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 History Discovery Johan August Arfwedson (1817) First isolation William Thomas Brande (1821) 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%. v t e · references Lithium (from Greek: λίθος lithos, "stone") is a chemical element with symbol Li and atomic number 3. It is a soft, silver-white metal belonging to the alkali metal group of chemical elements. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable. For this reason, it is typically stored in mineral oil. When cut open, lithium exhibits a metallic luster, but contact with moist air corrodes the surface quickly to a dull silvery gray, then black tarnish. Because of its high reactivity, lithium never occurs freely in nature, and instead, only appears in compounds, which are usually ionic. Lithium occurs in a number of pegmatitic minerals, but due to its solubility as an ion is present in ocean water and is commonly obtained from brines and clays. On a commercial scale, lithium is isolated electrolytically from a mixture of lithium chloride and potassium chloride. The nuclei of lithium verge on instability, since the two stable lithium isotopes found in nature have among the lowest binding energies per nucleon of all stable nuclides. Because of its relative nuclear instability, lithium is less common in the solar system than 25 of the first 32 chemical elements even though the nuclei are very light in atomic weight.[1] For related reasons, lithium has important links to nuclear physics. The transmutation of lithium atoms to helium in 1932 was the first fully man-made nuclear reaction, and lithium-6 deuteride serves as a fusion fuel in staged thermonuclear weapons.[2] Lithium and its compounds have several industrial applications, including heat-resistant glass and ceramics, high strength-to-weight alloys used in aircraft, lithium batteries and lithium-ion batteries. These uses consume more than half of lithium production. Trace amounts of lithium are present in all organisms. The element serves no apparent vital biological function, since animals and plants survive in good health without it. Non-vital functions have not been ruled out. The lithium ion Li+ administered as any of several lithium salts has proved to be useful as a mood-stabilizing drug in the treatment of bipolar disorder, due to neurological effects of the ion in the human body. Contents [hide] 1 Properties 1.1 Atomic and physical 1.2 Chemistry and compounds 1.3 Isotopes 2 Occurrence 2.1 Astronomical 2.2 Terrestrial 2.3 Biological 3 History 4 Production 5 Uses 5.1 Ceramics and glass 5.2 Electrical and electronics 5.3 Lubricating greases 5.4 Metallurgy 5.5 Other chemical and industrial uses 5.6 Nuclear 5.7 Medicine 6 Precautions 6.1 Regulation 7 See also 8 Notes 9 References 10 External links Properties[edit] Main article: Alkali metal Atomic and physical[edit] alt1 alt2 Lithium pellets covered in white lithium hydroxide (left) and ingots with a thin layer of black nitride tarnish (right) Like the other alkali metals, lithium has a single valence electron that is easily given up to form a cation.[3] Because of this, it is a good conductor of heat and electricity as well as a highly reactive element, though the least reactive of the alkali metals. Lithium's low reactivity compared to other alkali metals is due to the proximity of its valence electron to its nucleus (the remaining two electrons are in lithium's 1s orbital and are much lower in energy, and therefore they do not participate in chemical bonds).[3] Lithium metal is soft enough to be cut with a knife. When cut, it possesses a silvery-white color that quickly changes to gray due to oxidation.[3] While it has one of the lowest melting points among all metals (180 °C), it has the highest melting and boiling points of the alkali metals.[4] Lithium has a very low density of 0.534 g/cm3, comparable with that of pine wood. It is the least dense of all elements that are solids at room temperature, the next lightest solid element (potassium, at 0.862 g/cm3) being more than 60% denser. Furthermore, apart from helium and hydrogen, it is less dense than any liquid element, being only 2/3 as dense as liquid nitrogen (0.808 g/cm3).[note 1][5] Lithium can float on the lightest hydrocarbon oils and is one of only three metals that can float on water, the other two being sodium and potassium. Lithium floating in oil Lithium's coefficient of thermal expansion is twice that of aluminium and almost four times that of iron.[6] It has the highest specific heat capacity of any solid element. Lithium is superconductive below 400 μK at standard pressure[7] and at higher temperatures (more than 9 K) at very high pressures (>20 GPa)[8] At temperatures below 70 K, lithium, like sodium, undergoes diffusionless phase change transformations. At 4.2 K it has a rhombohedral crystal system (with a nine-layer repeat spacing); at hi