Mercury (element)?

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80 gold ← mercury → thallium Cd ↑ Hg ↓ Uub periodic table
General
Name, Symbol, Number	mercury, Hg, 80
Chemical series	transition metals
Group, Period, Block	12, 6, d
Appearance	silvery white
Atomic mass	200.59(2) g/mol
Electron configuration	Xe 4f14 5d10 6s2
Electrons per shell	2, 8, 18, 32, 18, 2
Physical properties
Phase	liquid
Density (near r.t.)	(liquid) 13.534 g/cm³
Melting point	234.32 K (-38.83 °C, -37.89 °F)
Boiling point	629.88 K (356.73 °C, 674.11 °F)
Heat of fusion	2.29 kJ/mol
Heat of vaporization	59.11 kJ/mol
Heat capacity	(25 °C) 27.983 J/(mol·K)
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K 315 350 393 449 523 629
Atomic properties
Crystal structure	rhombohedral
Oxidation states	2, 1 (mildly basic oxide)
Electronegativity	2.00 (Pauling scale)
Ionization energies	1st: 1007.1 kJ/mol
	2nd: 1810 kJ/mol
	3rd: 3300 kJ/mol
Atomic radius	150 pm
Atomic radius (calc.)	171 pm
Covalent radius	149 pm
Van der Waals radius	155 pm
Miscellaneous
Magnetic ordering	diamagnetic
Electrical resistivity	(25 °C) 961 nΩ·m
Thermal conductivity	(300 K) 8.30 W/(m·K)
Thermal expansion	(25 °C) 60.4 µm/(m·K)
Speed of sound	(liquid, 20 °C) 1451.4 m/s
CAS registry number	7439-97-6
Notable isotopes
Main article: Isotopes of mercury iso NA half-life DM DE (MeV) DP 194Hg syn 444 y ε 0.040 194Au 195Hg syn 9.9 h ε 1.510 195Au 196Hg 0.15% Hg is stable with 116 neutrons 197Hg syn 64.14 h ε 0.600 197Au 198Hg 9.97% Hg is stable with 118 neutrons 199Hg 16.87% Hg is stable with 119 neutrons 200Hg 23.1% Hg is stable with 120 neutrons 201Hg 13.18% Hg is stable with 121 neutrons 202Hg 29.86% Hg is stable with 122 neutrons 203Hg syn 46.612 d β- 0.492 203Tl 204Hg 6.87% Hg is stable with 124 neutrons
References

Mercury, also called quicksilver, is a chemical element in the periodic table that has the symbol Hg (from the Greek hydrargyrum, for watery (or liquid) silver) and atomic number 80. A heavy, silvery, transition metal, mercury is one of five elements that are liquid at or near room temperature (the others are the metals caesium, francium, and gallium, and the nonmetal bromine). Mercury is used in thermometers, barometers and other scientific apparatuses, although the use of mercury in thermometers has been largely phased out in clinical and scientific environments (in favor of alcohol-filled, digital or thermistor-based replacements) in the interests of health and safety due to the toxicity of the element. Mercury is mostly obtained by reduction from the mineral cinnabar.

Notable characteristics

Mercury is a relatively poor conductor of heat but is a good conductor of electricity.

Mercury easily forms alloys with almost all common metals, including gold, aluminium, and silver, but not iron. Tellurium forms an alloy also, but it reacts slowly to form mercury telluride. Any of these alloys is called an amalgam.

This metal also has uniform volumetric thermal expansion, is less reactive than zinc and cadmium and does not displace hydrogen from acids. Common oxidation states of this element are +1 and +2. Rare instances of +3 mercury compounds exist.

The commercial unit for handling mercury is the "flask," which weighs 76 lb (34.5 kg).

Applications

Mercury is used primarily for the manufacture of industrial chemicals or for electrical and electronic applications. It is used in some thermometers, especially ones which are used to measure high temperatures (Non-prescription sale of mercury fever thermometers was banned by a number of different states and localities). Other uses:

• Mercury sphygmomanometers (banned in some states and hospitals).
• Thimerosal, an organic compound used as a preservative in vaccines and tattoo inks (Thimerosal in vaccines).
• Mercury barometers, diffusion pumps, coulometers, and many other laboratory instruments. As an opaque liquid with a very high density, it is ideal for this role
• The triple point of mercury, -38.8344 °C, is a fixed point used as a temperature standard for the International Temperature Scale (ITS-90).
• In some gaseous electron tubes, mercury arc rectifier
• Gaseous mercury is used in mercury-vapor lamps and some "neon sign" type advertising signs and fluorescent lamps.
• Mercury was once used in the amalgamation process of refining gold and silver ores. The practice is continued by the garimpeiros (gold miners) of the Amazon basin in Brazil.
• Mercury is still used in some cultures for folk medicine and ceremonial purposes which may involve ingestion, injection, or the sprinkling of elemental mercury around the home.

Miscellaneous uses: mercury switches, mercury cells for sodium hydroxide and chlorine production, electrodes in some types of electrolysis, batteries (mercury cells), and catalysts, herbicides (discontinued in 1995), insecticides, dental amalgams/preparations and liquid mirror telescopes.

Historical uses: preserving wood, developing daguerreotypes, silvering mirrors, anti-fouling paints (discontinued in 1990), cleaning, and in road leveling devices in cars. Mercury compounds have been used in antiseptics, laxatives, antidepressants, and antisyphilitics. It was also allegedly used by allied spies to sabotage German planes. A mercury paste was applied on bare aluminum, causing the metal to rapidly corrode. This would cause the planes to mysteriously fall apart.

History

Mercury was known to the ancient Chinese and Hindus and was found in Egyptian tombs that date from 1500 BCE. In China, India and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health. The ancient Greeks used mercury in ointments and the Romans used it in cosmetics. By 500 BCE mercury was used to make amalgams with other metals.

The Indian word for alchemy is Rassayana which means ‘the way of mercury.’ Alchemists often thought of mercury as the first matter from which all metals were formed. Different metals could be produced by varying the quality and quantity of sulfur contained within the mercury. An ability to transform mercury into any metal resulted from the essentially mercurial quality of all metals. The purest of these was gold, and mercury was required for the transmutation of base (or impure) metals into gold. This was a primary goal of alchemy, either for material or spiritual gain.

Hg is the modern chemical symbol for mercury. It comes from hydrargyrum, a Latinized form of the Greek word `Υδραργυρος (hydrargyros), which is a compound word meaning 'water' and 'silver' — since it is liquid, like water, and yet has a silvery metallic sheen. The element was named after the Roman god Mercury, known for speed and mobility. It is associated with the planet Mercury. The astrological symbol for the planet is also one of the alchemical symbols for the metal (above left). Mercury is the only metal for which the alchemical planetary name became the common name.

From the mid-18th to the mid-19th centuries, a process called "carroting" was used in the making of felt hats. Animal skins were rinsed in an orange solution of the mercury compound mercuric nitrate, Hg(NO₃)₂•2H₂O. This process separated the fur from the pelt and matted it together. This solution and the vapors it produced were highly toxic. Its use resulted in widespread cases of mercury poisoning among hatters. Symptoms included tremors, emotional lability, insomnia, dementia and hallucinations. The United States Public Health Service banned the use of mercury in the felt industry in December 1941. The psychological symptoms associated with mercury poisoning may have inspired the simile "mad as a hatter", and thereby the Mad Hatter of Alice in Wonderland fame.

Dentistry

Elemental mercury is the main ingredient in dental amalgams. Controversy over the health effects from the use of mercury amalgams began shortly after its introduction into the western world, nearly 200 years ago. In 1843, The American Society of Dental Surgeons, concerned about mercurial poisoning, required its members to sign a pledge that they would not use amalgam. In 1859, The American Dental Association was formed by dentists who believed amalgam was, "safe and effective." The ADA, "continues to believe that amalgam is a valuable, viable and safe choice for dental patients," as written in their statement on dental amalgam . In 1993, the United States Public Health Service reported that, "amalgam fillings release small amounts of mercury vapor," but in such a small amount that it, "has not been shown to cause any … adverse health effects." In 2002, California became the first state to ban the future use of mercury fillings (effective 2006). As of 2005, the controversy continues.

Medicine

Mercury has been used in the treatment of illnesses for centuries. Mercury(I) chloride and mercury(II) chloride were popular compounds. Mercury was included in the treatment of syphilis as early as the 16th century, before the advent of antibiotics. "Blue mass," a small pill in which mercury is the main ingredient, was prescribed throughout the 1800s for numerous conditions including, constipation, depression, child-bearing and toothaches (National Geographic). In the early 20th century, mercury was administered to children yearly as a laxative and dewormer. It was a teething powder for infants and some vaccines have contained the preservative Thimerosal (partly ethyl mercury) since the 1930s (FDA report). Mercury(II) chloride was a disinfectant for doctors, patients and instruments.

Mercury in the form of cinnabar remains an important component of Chinese, Tibetan, and Ayurvedic medicine. As problems may arise when these medicines are exported to countries that prohibit the use of mercury in medicines, in recent times, less toxic substitutes have been devised.

Today, mercuric medicines and devices are generally considered hazardous. Neither are used to the extent they were in the past. Thermometers and sphygmomanometers containing mercury were invented in the early 18th and late 19th centuries, respectively. In the early 21st century, their use is declining and has been banned in some countries, states and medical institutions. In 2002, the U.S. Senate passed legislation to phase out the sale of non-prescription mercury thermometers. In 2003, Washington and Maine became the first states to ban mercury blood pressure devices (HCWH News release). In 2005, mercury compounds are found in some OTC medications, including, topical antiseptics, stimulant laxatives, diaper rash ointment, eye drops and nose sprays. The FDA has "inadequate data to establish general recognition of the safety and effectiveness," of the mercury ingredients in these products (Code of federal regulations).

Mineral occurrence

Mercury ore