Lithium (from Greek: λίθος, romanized: lithos, lit.'stone') is a chemical element with the 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 or mineral oil. When cut, it exhibits a metallic luster, but moist air corrodes it quickly to a dull silvery gray, then black tarnish. It never occurs freely in nature, but only in (usually ionic) compounds, such 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.

Lithium, 3Li
Lithium floating in oil
Pronunciation/ˈlɪθiəm/ (LITH-ee-əm)
Standard atomic weight Ar°(Li)
  • [6.938, 6.997]
  • 6.94±0.06 (abridged)[1]
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


Atomic number (Z)3
Groupgroup 1: hydrogen and alkali metals
Periodperiod 2
Block  s-block
Electron configuration[He] 2s1
Electrons per shell2, 1
Physical properties
Phase at STPsolid
Melting point453.65 K (180.50 °C, 356.90 °F)
Boiling point1603 K (1330 °C, 2426 °F)
Density (near r.t.)0.534 g/cm3
when liquid (at m.p.)0.512 g/cm3
Critical point3220 K, 67 MPa (extrapolated)
Heat of fusion3.00 kJ/mol
Heat of vaporization136 kJ/mol
Molar heat capacity24.860 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+1 (a strongly basic oxide)
ElectronegativityPauling scale: 0.98
Ionization energies
  • 1st: 520.2 kJ/mol
  • 2nd: 7298.1 kJ/mol
  • 3rd: 11815.0 kJ/mol
Atomic radiusempirical: 152 pm
Covalent radius128±7 pm
Van der Waals radius182 pm
Spectral lines of lithium
Other properties
Natural occurrenceprimordial
Crystal structure body-centered cubic (bcc)
Speed of sound thin rod6000 m/s (at 20 °C)
Thermal expansion46 µm/(m⋅K) (at 25 °C)
Thermal conductivity84.8 W/(m⋅K)
Electrical resistivity92.8 nΩ⋅m (at 20 °C)
Magnetic orderingparamagnetic
Molar magnetic susceptibility+14.2×10−6 cm3/mol (298 K)[2]
Young's modulus4.9 GPa
Shear modulus4.2 GPa
Bulk modulus11 GPa
Mohs hardness0.6
Brinell hardness5 MPa
CAS Number7439-93-2
DiscoveryJohan August Arfwedson (1817)
First isolationWilliam Thomas Brande (1821)
Main isotopes of lithium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
6Li 7.59% stable
7Li 92.41% stable
 Category: Lithium
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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.[3] For related reasons, lithium has important uses in nuclear physics. The transmutation of lithium atoms to helium in 1932 was the first fully man-made nuclear reaction, and lithium deuteride serves as a fusion fuel in staged thermonuclear weapons.[4]

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 batteries, and lithium-ion batteries. These uses consume more than three-quarters of lithium production.

Lithium is present in biological systems in trace amounts; its functions are uncertain. Lithium salts have proven to be useful as a mood stabilizer and antidepressant in the treatment of mental illness such as bipolar disorder.

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