Mercury (element)

Mercury, 80Hg
Pouring liquid mercury bionerd.jpg
Mercury
Appearancesilvery
Standard atomic weight Ar, std(Hg)200.592(3)[1]
Mercury in the periodic table
HydrogenHelium
LithiumBerylliumBoronCarbonNitrogenOxygenFluorineNeon
SodiumMagnesiumAluminiumSiliconPhosphorusSulfurChlorineArgon
PotassiumCalciumScandiumTitaniumVanadiumChromiumManganeseIronCobaltNickelCopperZincGalliumGermaniumArsenicSeleniumBromineKrypton
RubidiumStrontiumYttriumZirconiumNiobiumMolybdenumTechnetiumRutheniumRhodiumPalladiumSilverCadmiumIndiumTinAntimonyTelluriumIodineXenon
CaesiumBariumLanthanumCeriumPraseodymiumNeodymiumPromethiumSamariumEuropiumGadoliniumTerbiumDysprosiumHolmiumErbiumThuliumYtterbiumLutetiumHafniumTantalumTungstenRheniumOsmiumIridiumPlatinumGoldMercury (element)ThalliumLeadBismuthPoloniumAstatineRadon
FranciumRadiumActiniumThoriumProtactiniumUraniumNeptuniumPlutoniumAmericiumCuriumBerkeliumCaliforniumEinsteiniumFermiumMendeleviumNobeliumLawrenciumRutherfordiumDubniumSeaborgiumBohriumHassiumMeitneriumDarmstadtiumRoentgeniumCoperniciumNihoniumFleroviumMoscoviumLivermoriumTennessineOganesson
Cd

Hg

Cn
goldmercurythallium
Atomic number (Z)80
Groupgroup 12
Periodperiod 6
Blockd-block
Element category  Post-transition metal, alternatively considered a transition metal
Electron configuration[Xe] 4f14 5d10 6s2
Electrons per shell2, 8, 18, 32, 18, 2
Physical properties
Phase at STPliquid
Melting point234.3210 K ​(−38.8290 °C, ​−37.8922 °F)
Boiling point629.88 K ​(356.73 °C, ​674.11 °F)
Density (near r.t.)13.534 g/cm3
Triple point234.3156 K, ​1.65×10−7 kPa
Critical point1750 K, 172.00 MPa
Heat of fusion2.29 kJ/mol
Heat of vaporization59.11 kJ/mol
Molar heat capacity27.983 J/(mol·K)
Vapor pressure
P (Pa)1101001 k10 k100 k
at T (K)315350393449523629
Atomic properties
Oxidation states−2 , +1 (mercurous), +2 (mercuric) (a mildly basic oxide)
ElectronegativityPauling scale: 2.00
Ionization energies
  • 1st: 1007.1 kJ/mol
  • 2nd: 1810 kJ/mol
  • 3rd: 3300 kJ/mol
Atomic radiusempirical: 151 pm
Covalent radius132±5 pm
Van der Waals radius155 pm
Color lines in a spectral range
Spectral lines of mercury
Other properties
Natural occurrenceprimordial
Crystal structurerhombohedral
Rhombohedral crystal structure for mercury
Speed of soundliquid: 1451.4 m/s (at 20 °C)
Thermal expansion60.4 µm/(m·K) (at 25 °C)
Thermal conductivity8.30 W/(m·K)
Electrical resistivity961 nΩ·m (at 25 °C)
Magnetic orderingdiamagnetic[2]
Magnetic susceptibility−33.44·10−6 cm3/mol (293 K)[3]
CAS Number7439-97-6
History
DiscoveryAncient Egyptians (before 1500 BCE)
Main isotopes of mercury
Iso­topeAbun­danceHalf-life (t1/2)Decay modePro­duct
194Hgsyn444 yε194Au
195Hgsyn9.9 hε195Au
196Hg0.15%stable
197Hgsyn64.14 hε197Au
198Hg10.04%stable
199Hg16.94%stable
200Hg23.14%stable
201Hg13.17%stable
202Hg29.74%stable
203Hgsyn46.612 dβ203Tl
204Hg6.82%stable
| references

Mercury is a chemical element with the symbol Hg and atomic number 80. It is commonly known as quicksilver and was formerly named hydrargyrum (m/ DRAR-jər-əm).[4] A heavy, silvery d-block element, mercury is the only metallic element that is liquid at standard conditions for 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.

Mercury remains in use in scientific research applications and in amalgam for dental restoration in some locales. 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.

Properties

Physical properties

A pound coin (density ~7.6 g/cm3) floats in mercury due to the combination of the buoyant force and surface tension.

Mercury is a heavy, silvery-white liquid metal. Compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity.[5]

It has a freezing point of −38.83 °C and a boiling point of 356.73 °C,[6][7][8] both the lowest of any stable metal, although preliminary experiments on copernicium and flerovium have indicated that they have even lower boiling points (copernicium being the element below mercury in the periodic table, following the trend of decreasing boiling points down group 12).[9] Upon freezing, the volume of mercury decreases by 3.59% and its density changes from 13.69 g/cm3 when liquid to 14.184 g/cm3 when solid. The coefficient of volume expansion is 181.59 × 10−6 at 0 °C, 181.71 × 10−6 at 20 °C and 182.50 × 10−6 at 100 °C (per °C). Solid mercury is malleable and ductile and can be cut with a knife.[10]

A complete explanation of mercury's extreme volatility delves deep into the realm of quantum physics, but it can be summarized as follows: mercury has a unique electron configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d, and 6s subshells. Because this configuration strongly resists removal of an electron, mercury behaves similarly to noble gases, which form weak bonds and hence melt at low temperatures.

The stability of the 6s shell is due to the presence of a filled 4f shell. An f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus (see lanthanide contraction). The absence of a filled inner f shell is the reason for the somewhat higher melting temperature of cadmium and zinc, although both these metals still melt easily and, in addition, have unusually low boiling points.[6][7]

Chemical properties

Mercury does not react with most acids, such as dilute sulfuric acid, although oxidizing acids such as concentrated sulfuric acid and nitric acid or aqua regia dissolve it to give sulfate, nitrate, and chloride. Like silver, mercury reacts with atmospheric hydrogen sulfide. Mercury reacts with solid sulfur flakes, which are used in mercury spill kits to absorb mercury (spill kits also use activated carbon and powdered zinc).[11]

Amalgams

Mercury-discharge spectral calibration lamp

Mercury dissolves many metals such as gold and silver to form amalgams. Iron is an exception, and iron flasks have traditionally been used to trade mercury. Several other first row transition metals with the exception of manganese, copper and zinc are also resistant in forming amalgams. Other elements that do not readily form amalgams with mercury include platinum.[12][13] Sodium amalgam is a common reducing agent in organic synthesis, and is also used in high-pressure sodium lamps.

Mercury readily combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact. Since the amalgam destroys the aluminium oxide layer which protects metallic aluminium from oxidizing in-depth (as in iron rusting), even small amounts of mercury can seriously corrode aluminium. For this reason, mercury is not allowed aboard an aircraft under most circumstances because of the risk of it forming an amalgam with exposed aluminium parts in the aircraft.[14]

Mercury embrittlement is the most common type of liquid metal embrittlement.

Isotopes

There are seven stable isotopes of mercury, with 202
Hg
being the most abundant (29.86%). The longest-lived radioisotopes are 194
Hg
with a half-life of 444 years, and 203
Hg
with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives that are less than a day. 199
Hg
and 201
Hg
are the most often studied NMR-active nuclei, having spins of ​12 and ​32 respectively.[5]