Mercury (Hg)

Stable isotopes of mercury available from ISOFLEX

Isotope Z(p) N(n) Atomic Mass Natural Abundance Enrichment Level Chemical Form
Hg-196  80  116  195.965814 0.15%  51.00-95.00% Metal
Hg-196 80 116 195.965814 0.15% 51.00-95.00% Oxide
Hg-198 80 118 197.966752 9.97% 94.00-99.00% Metal
Hg-198 80 118 197.966752 9.97% 94.00-99.00% Oxide
Hg-199 80 119 198.968262 16.87% ≥90.00% Metal
Hg-199 80 119 198.968262 16.87% ≥90.00% Oxide
Hg-200 80 120 199.968309 23.10% ≥95.00% Metal
Hg-200 80 120 199.968309 23.10% ≥95.00% Oxide
Hg-202 80 122 201.970625 29.86% ≥99.00% Metal
Hg-202 80 122 201.970625 29.86% ≥99.00% Oxide
Hg-204  80  124  203.973475 6.87%  ≥96.00%  Metal
Hg-204 80 124 203.973475 6.87% ≥96.00% Oxide

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Mercury was known and used in ancient civilizations. It has been found in Egyptian tombs dated from 1500 BC; the Greeks used it in ointments; and the Romans used it in cosmetics. It is named for the planet Mercury, and its symbol, Hg, originates with the Latin word hydrargyrum, meaning “liquid silver.”

Mercury is an extremely heavy liquid, the only metal and one of only two elements that naturally occur as a liquid in ambient temperatures. It does not wet glass, and it forms tiny globules. It is insoluble in hydrochloric acid, water, alcohol and ether; soluble in sulfuric acid upon boiling; and readily soluble in nitric acid and lipids. Mercury is stable in dry air or oxygen at ordinary temperatures; however, in the presence of moisture, oxygen slowly attacks the metal, forming red mercury(II) oxide. When the metal is heated in air or oxygen (to about 350 ºC), it is gradually converted to its oxide. Mercury readily combines with halogens at ordinary temperatures, forming mercury(II) halides. Its metal forms both mercury(I) and mercury(II) salts. Dilute sulfuric acid has no effect on the metal; nor does air-free hydrochloric acid. Water has no effect on mercury; nor does molecular hydrogen. However, atomic hydrogen readily combines with mercury vapors when exposed to radiation from a mercury arc, forming hydride.

Some of the most important uses of mercury are in the electrical and electrolytic industries, including batteries and cells in portable radios, microphones, cameras, hearing aids, watches, smoke alarms, wiring and switching devices, mercury vapor lamps, fluorescent tubes, electrical discharge tubes, and mercury electrodes in electrolytic cells. Mercury cathodes are employed in the electrolysis of sodium chloride to produce caustic soda and chlorine. Another major use is in thermometers, manometers, barometers and other pressure-sensing devices. Mercury is also used as a catalyst in making urethane foams and vinyl chloride monomers; elemental mercury and its compounds have long been used as fungicides in paints and in agriculture; and its compounds are used in medicines, pigments and analytical reagents.

Elemental mercury and all of its compounds are highly toxic by all routes of exposure. The element has significant vapor pressure at ambient temperatures that can produce a severe inhalation hazard. Symptoms from short exposure to high concentrations of mercury vapors include bronchitis, coughing, chest pain, respiratory distress, salivation, diarrhea, tremors, insomnia and depression. Mercury can cause damage to the kidneys, liver, lungs and brain. Organomercury compounds and inorganic salt solutions can be absorbed into the body through skin contact, causing severe poisoning. It accumulates as Hg2+ in the brain and kidneys. The United States Environmental Protection Agency has classified mercury as one of the priority pollutant metals.

Properties of Mercury

Name Mercury 
Symbol Hg 
Atomic number 80 
Atomic weight 200.59
Standard state Liquid at 298 ºK (the heaviest known element liquid) 
CAS Registry ID 7439-97-6
Group in periodic table 12 
Group name None 
Period in periodic table
Block in periodic table d-block 
Color Silvery white 
Classification Metallic 
Melting point -38.842 °C
Boiling point 356.58 °C
Thermal conductivity 8.3 W/(m·K) at 298.2 °K
Electrical resistivity 98.4 µΩ·cm at 50 °C 
Electronegativity 1.9 
Specific heat 0.14 kJ/kg K
Heat of vaporization

59.0 kJ·mol-1 at 356.58 °C

Heat of fusion

11.3 kJ/kg

Density of liquid 13.53 g/cm3
Electron configuration [Xe]4f145d106s2 
Atomic radius 1.51 Å
Ionic radius Hg2+: 1.16 Å (coordination number 6)
Ionization potential 10.437 eV (1st) and 18.756 eV (2nd)
Oxidation states  +1, +2 
Critical temperature  1477 ºC 
Critical pressure  732 atm 
Critical volume  43 cm3/mol 

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