Lithium

Lithium, ₃Li

Freshly cut sample of lithium, with minimal oxides
Lithium
Pronunciation	/ˈlɪθiəm/ ​(LITH-ee-əm)
Appearance	silvery-white
Standard atomic weight Ar°(Li)
	[6.938, 6.997][1] 6.94±0.06 (abridged)[2]
Lithium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson H ↑ Li ↓ Na helium ← lithium → beryllium
Atomic number (Z)	3
Group	group 1: hydrogen and alkali metals
Period	period 2
Block	s-block
Electron configuration	[He] 2s1
Electrons per shell	2, 1
Physical properties
Phase at STP	solid
Melting point	453.65 K ​(180.50 °C, ​356.90 °F)
Boiling point	1603 K ​(1330 °C, ​2426 °F)
Density (at 20° C)	0.5334 g/cm3[3]
when liquid (at m.p.)	0.512 g/cm3
Critical point	3220 K, 67 MPa (extrapolated)
Heat of fusion	3.00 kJ/mol
Heat of vaporization	136 kJ/mol
Molar heat capacity	24.860 J/(mol·K)
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	common: +1 −1[4]
Electronegativity	Pauling scale: 0.98
Ionization energies	1st: 520.2 kJ/mol 2nd: 7298.1 kJ/mol 3rd: 11815.0 kJ/mol
Atomic radius	empirical: 152 pm
Covalent radius	128±7 pm
Van der Waals radius	182 pm
Spectral lines of lithium
Other properties
Natural occurrence	primordial
Crystal structure	​body-centered cubic (bcc) (cI2)
Lattice constant	a = 350.93 pm (at 20 °C)[3]
Thermal expansion	46.56×10−6/K (at 20 °C)[3]
Thermal conductivity	84.8 W/(m⋅K)
Electrical resistivity	92.8 nΩ⋅m (at 20 °C)
Magnetic ordering	paramagnetic
Molar magnetic susceptibility	+14.2×10−6 cm3/mol (298 K)[5]
Young's modulus	4.9 GPa
Shear modulus	4.2 GPa
Bulk modulus	11 GPa
Speed of sound thin rod	6000 m/s (at 20 °C)
Mohs hardness	0.6
Brinell hardness	5 MPa
CAS Number	7439-93-2
History
Discovery	Johan August Arfwedson (1817)
First isolation	William Thomas Brande (1821)
Isotopes of lithium v e
Main isotopes[6] Decay abun­dance half-life (t1/2) mode pro­duct 6Li [1.9%, 7.8%] Preview warning: Infobox Li isotopes: Abundance percentage not recognised "na=[1.9%, 7.8%]" cat#% stable 7Li [92.2%, 98.1%] Preview warning: Infobox Li isotopes: Abundance percentage not recognised "na=[92.2%, 98.1%]" cat#% stable Significant variation occurs in commercial samples because of the wide distribution of samples depleted in 6Li.
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Lithium (from Ancient Greek λίθος (líthos) 'stone') is a chemical element; it has symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable, and must be stored in vacuum, inert atmosphere, or inert liquid such as purified kerosene^[7] or mineral oil. It exhibits a metallic luster. It corrodes quickly in air to a dull silvery gray, then black tarnish. It does not occur freely in nature, but occurs mainly as pegmatitic minerals, which were once the main source of lithium. Due to its solubility as an ion, it is present in ocean water and is commonly obtained from brines. Lithium metal is isolated electrolytically from a mixture of lithium chloride and potassium chloride.

The nucleus of the lithium atom verges 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 its nuclei are very light: it is an exception to the trend that heavier nuclei are less common.^[8] For related reasons, lithium has important uses in nuclear physics. The transmutation of lithium atoms to helium in 1932 was the first fully human-made nuclear reaction, and lithium deuteride serves as a fusion fuel in staged thermonuclear weapons.^[9]

Lithium and its compounds have several industrial applications, including heat-resistant glass and ceramics, lithium grease lubricants, flux additives for iron, steel and aluminium production, lithium metal batteries, and lithium-ion batteries. These uses consume more than three-quarters of lithium production.^{[citation needed][when?]}

Lithium is present in biological systems in trace amounts. It has no established metabolic function in humans. Lithium-based drugs are useful as a mood stabilizer and antidepressant in the treatment of mental illness such as bipolar disorder.