Lithium (from Ancient Greek λίθος (líthos) '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. 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. 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. 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. Lithium is present in biological systems in trace amounts. It has no established metabolic function. Lithium-based drugs are useful as a mood stabilizer and antidepressant in the treatment of mental illness such as bipolar disorder.

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Atomic properties

Standard atomic weight6.94 ±0.06 [6.938 … 6.997]
Atomic mass6.946 u

Atomic radii

Radius (empirical)152 pm
Radius (calculated)167 pm
Covalent radius128 ±7 pm
Van der Waals radius182 pm

Atomic shell

Electron configurationHe 2s1
Ionization energy(1st) 5.3917149 eV
(2nd) 75.640096 eV
(3rd) 122.45435 eV
Shell model

Physical properties

Density0.534 g·cm−3 (293.1 K)
Molar volume1.302·10-5 m3·mol−1
Speed of sound6,000 m·s−1 (293.1 K)


Melting point453.6 K
Boiling point1,603 K
Liquid range1,149 K
Critical point(3,220 K @ 67 MPa)
Transition temperature20 K


Melting enthalpy3 kJ·mol-1
Enthalpy of vaporization147 kJ·mol-1
Binding energy159 kJ·mol-1

Heat and conductivity

Specific heat capacity3,482 J·kg−1·K−1
Thermal conductivity85 W·m-1·K-1
Expansion coefficient4.6·10-5 K-1
Work function2.9 eV


Mohs hardness0.6

Elastic properties

Young’s modulus4.9 GPa
Shear modulus4.2 GPa
Bulk modulus11 GPa

Electrical properties

Electrical conductivity1.06·107 S·m-1
Resistance9.5·10-8 Ωm


Magnetic susceptibility1.42·10-5 cm3·mol−1 (298 K)

Other properties

Natural occurrenceprimordial
Crystal structureBody-centered cubic
Goldschmidt Classificationlithophile
Superconductorwith transition tempperature under special conditions
Price/kg83.5 USD

Natural abundances

6 ppb ≈ 6.03·1010 M☉
0.06 ppb ≈ 1.19·108 Mt
1,700 ppb ≈ 1.7 g
Earth’s crust
17,000 ppb ≈ 470,000 Mt
180 ppb ≈ 246 Gt
Flowing water
3,000 ppb ≈ 48 Gt
Human body
30 ppb ≈ 2.1 mg