Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver and was formerly named hydrargyrum ( hy-DRAR-jər-əm) from the Greek words hydro (water) and argyros (silver). A heavy, silvery d-block element, mercury is the only metallic element that is known to be liquid at standard temperature and pressure; the only other element that is liquid under these conditions is the halogen bromine, though metals such as caesium, gallium, and rubidium melt just above room temperature.

Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide). The red pigment vermilion is obtained by grinding natural cinnabar or synthetic mercuric sulfide.

Mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, mercury switches, mercury relays, fluorescent lamps and other devices, though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favor of alternatives such as alcohol- or galinstan-filled glass thermometers and thermistor- or infrared-based electronic instruments. Likewise, mechanical pressure gauges and electronic strain gauge sensors have replaced mercury sphygmomanometers. The mercury cell process (chlor-alkali) is used to produce chlorine and sodium or potassium hydroxide, but is phased out.

Mercury, and mercury compounds, remain in use in scientific research applications and in amalgam for dental restoration in some locales, and in some food manufacturing operations. In food manufacturing, mercuric chloride is used in the starch extraction process during rice, corn, and wheat refining to inhibit starch degrading enzymes. It is also used in fluorescent lighting. Electricity passed through mercury vapor in a fluorescent lamp produces short-wave ultraviolet light, which then causes the phosphor in the tube to fluoresce, making visible light.

Mercury poisoning can result from exposure to water-soluble forms of mercury (such as mercuric chloride or methylmercury), by inhalation of mercury vapor, or by ingesting any form of mercury. In serious form, it is also known as Minamata disease. Mercury poisoning is intensified with lead co-exposures.

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Atomic properties

Standard atomic weight200.592 ±0.003
Atomic mass200.592 u

Atomic radii

Radius (empirical)151 pm
Radius (calculated)171 pm
Covalent radius132 ±5 pm
Van der Waals radius155 pm

Atomic shell

Electron configurationXe 4f14 5d10 6s2
Ionization energy(1st) 10.437504 eV
(2nd) 18.75687 eV
(3rd) 34.49 eV
(4th) 48.55 eV
(5th) 61.2 eV
Shell model

Physical properties

Density13.54 g·cm−3 (293.1 K)
Molar volume1.409·10-5 m3·mol−1
Speed of sound1,407 m·s−1 (293.1 K)


Melting point234.3 K
Boiling point629.8 K
Liquid range395.5 K
Triple point234.3 K @ 1.65·10-4 Pa
Critical point1,750 K @ 172 MPa
Transition temperature4.15 K


Melting enthalpy2.29 kJ·mol-1
Enthalpy of vaporization56.2 kJ·mol-1
Binding energy64 kJ·mol-1

Heat and conductivity

Specific heat capacity140 J·kg−1·K−1
Thermal conductivity8.3 W·m-1·K-1
Work function4.49 eV


Mohs hardness1.5

Elastic properties

Bulk modulus25 GPa

Electrical properties

Electrical conductivity1.04·106 S·m-1
Resistance9.6·10-7 Ωm



Optical properties

Reflectivity73 %
Refractive index1

Chemical properties

Basicityslightly basic
Oxidation state1, 2, 4
Standard potential0.8535 V (Hg2+ + 2e- → Hg)


Pauling scale2
Sanderson scale2.2
Allred-Rochow scale1.44
Mulliken scale1.81
Nagle scale1.54
Pearson absolute negativity4.91 eV

Other properties

Natural occurrenceprimordial
Crystal structureRhombohedral
Goldschmidt Classificationchalcophile
Superconductorwith transition tempperature (solid body, normal pressure)
Price/kg30.2 USD

Natural abundances

1 ppb ≈ 1·1010 M☉
20 ppb ≈ 3.97·1010 Mt
250 ppb ≈ 250 mg
Earth’s crust
67 ppb ≈ 1,850 Mt
0.05 ppb ≈ 68.5 kt
Flowing water
0.07 ppb ≈ 1.12 kt