Homeowork Help: DUE TOMORROW?

Question

please have compassion on a failing chem student
if u know anything about the chemical and physical properties, uses and other general info on mercury and oxygen then it would be heaps helpful

Answer 1

i procrastinate all the time. dont worry, ur not the only 1 w/ that habit. at room temperature, mercury's a liquid at room temperature, oxygen's a breathable gas that is a necessity for human life, the human body does not absorb mercury itself, and that's about all i no. hey, what do u expect from a fifth grader? and 4 me it's summer vacation! u have homework on july 4th?!?!?!

Answer 2

Hell, never do your homework earlier ah? What i suggest is to get one of your classmate and ask for "HELP", u know what i mean HEHEE..

Answer 3

General
Name, Symbol, Number oxygen, O, 8
Chemical series Nonmetals, chalcogens
Group, Period, Block 16, 2, p
Appearance very pale blue

Atomic mass 15.9994(3) g/mol
Electron configuration 1s2 2s2 2p4
Electrons per shell 2, 6
Physical properties
Phase gas
Density (0 °C, 101.325 kPa)
1.429 g/L
Template:Elementbox formation

Melting point 54.36 K
(-218.79 °C, -361.82 °F)
Boiling point 90.20 K
(-182.95 °C, -297.31 °F)
Critical point 154.59 K, 5.043 MPa
Heat of fusion (O2) 0.444 kJ/mol
Heat of vaporization (O2) 6.82 kJ/mol
Heat capacity (25 °C) (O2)
29.378 J/(mol·K)
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k
at T/K 61 73 90

Atomic properties
Crystal structure cubic
Oxidation states −2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJ/mol
2nd: 3388.3 kJ/mol
3rd: 5300.5 kJ/mol
Atomic radius 60 pm
Atomic radius (calc.) 48 pm
Covalent radius 73 pm
Van der Waals radius 152 pm
Miscellaneous
Magnetic ordering paramagnetic
Thermal conductivity (300 K) 26.58 mW/(m·K)
Speed of sound (gas, 27 °C) 330 m/s
CAS registry number 7782-44-7
Notable isotopes
Main article: Isotopes of oxygen iso NA half-life DM DE (MeV) DP
16O 99.76% O is stable with 8 neutrons
17O 0.038% O is stable with 9 neutrons
18O 0.21% O is stable with 10 neutrons

References
Oxygen is a chemical element. In the periodic table it has the symbol O and atomic number 8. Oxygen is the second most common element on Earth composing around 49% of the mass of Earth's crust[1] and 28% of the mass of Earth as a whole, and is the third most common element in the universe. On Earth, it is usually covalently or ionically bonded to other elements. Unbound oxygen (usually called molecular dioxygen, O2, a diatomic molecule) first appeared in significant quantities on Earth during the Paleoproterozoic era (between 2.5 billion years ago and 1.6 billion years ago) as a product of the metabolic action of early anaerobes (archaea and bacteria). This new presence of large amounts of free oxygen drove most of the organisms then living to extinction.[citation needed] The atmospheric abundance of free oxygen in later geological epochs and up to the present has been largely driven by photosynthetic organisms, roughly three quarters by phytoplankton and algae in the oceans and one quarter from terrestrial plants.

Characteristics
At standard temperature and pressure, oxygen exists as a diatomic molecule with the formula O2, in which the two oxygen atoms are doubly bonded to each other. In its most stable form, oxygen exists as a diradical (triplet oxygen). Though radicals are commonly associated with highly reactive compounds, triplet oxygen is surprisingly (and fortunately) unreactive towards most compounds. Singlet oxygen, a name given to several higher energy species in which all the electron spins are paired, is much more reactive towards common organic molecules. Carotenoids effectively absorb energy from singlet oxygen and convert it back into the unexcited ground state.

Oxygen is a major component of air, produced by plants during photosynthesis, and is necessary for aerobic respiration in animals. The word oxygen derives from two words in Greek, οξυς (oxys) (acid, sharp) and γεινομαι (geinomai) (engender). The name "oxygen" was chosen because, at the time it was discovered in the late 18th century, it was believed that all acids contained oxygen. The definition of acid has since been revised to not require oxygen in the molecular structure. Hydrochloric acid (HCl) does not contain oxygen. Liquid O2 and solid O2 have a light blue color and both are highly paramagnetic. Liquid O2 is usually obtained by the fractional distillation of liquid air. Liquid and solid O3 (ozone) have a deeper color of blue.

A recently discovered allotrope of oxygen, tetraoxygen (O4), is a deep red solid that is created by pressurizing O2 to the order of 20 GPa. Its properties are being studied for use in rocket fuels and similar applications, as it is a much more powerful oxidizer than either O2 or O3.[citation needed]

[edit]
Applications
Liquid oxygen finds use as an oxidizer in rocket propulsion. Oxygen is essential to respiration, so oxygen supplementation has found use in medicine (as oxygen therapy). People who climb mountains or fly in airplanes sometimes have supplemental oxygen supplies (to increase the inspired Oxygen partial pressure nearer to that found at sea-level requires increasing the proportion as a percentage of air). Oxygen is used in welding (such as the oxyacetylene torch), and in the making of steel and methanol.

Oxygen presents two absorption band centered in the wavelengths 687 and 760 nanometers. Some scientists have proposed to use the measurement of the radiance coming from vegetation canopies in those oxygen bands to characterize plant health status from a satellite platform.[citation needed] This is because in those bands, it is possible to discriminate the vegetation's reflectance from the vegetation's fluorescence, which is much weaker. The measurement presents several technical difficulties due to the low signal to noise ratio and due to the vegetation's architecture, but it has been proposed as a possibility to monitor the carbon cycle from satellites on a global scale.

Oxygen, as a mild euphoric, has a history of recreational[citation needed] use that extends into modern times. Oxygen bars can be seen at parties to this day. In the 19th century, oxygen was often mixed with nitrous oxide to promote an analgesic effect; a stable 50% gaseous mixture (Entonox) is commonly used in medicine today as an analgesic, and 30% oxygen with 70% Nitrous Oxide is the common basic anaesthetic mixture.

[edit]
Magnetic properties of liquid oxygen
Liquid oxygen displays some particularly interesting phenomena when exposed to a magnetic field. O2 molecules have an overall spin of 1, and therefore tend to align with an applied magnetic field, thus displaying paramagnetism. However, when in liquid form, neighbouring O2 molecules have a negative exchange energy and thus tend to align anti-parallel with each other. Consequently liquid oxygen shows anti-ferromagnetic behaviour, and has a magnetic susceptibility slightly lower than might be expected.

Liquid oxygen has a characteristic blue color in zero magnetic field. However, when exposed to a large magnetic field, it becomes colorless. This so called "field-transparency" effect occurs since the electronic transition which gives rise to the blue colour becomes forbidden in the spin polarised state.

When a pool of liquid oxygen is exposed to a sufficiently strong vertical magnetic field, the surface will sponaneously form a regular pattern of corrugations. The formation of the corrugations increases the surface free energy and the gravitational energy of the liquid, but reduces the overall magnetic energy.

[edit]
Scientific history
Oxygen was first discovered by Michał Sędziwój, a Polish alchemist and philosopher in the late 16th century. Sędziwój assumed the existence of oxygen by warming nitre (saltpeter). He thought of the gas given off as "the elixir of life".[citation needed]

Oxygen was again discovered by the Swedish pharmacist Carl Wilhelm Scheele sometime before 1773, but the discovery was not published until after the independent discovery by Joseph Priestley on August 1, 1774, who called the gas dephlogisticated air (see phlogiston theory). Priestley published discoveries in 1775 and Scheele in 1777; consequently Priestley is usually given the credit. It was named by Antoine Laurent Lavoisier after Priestley's publication in 1775.

[edit]
Occurrence
Annual mean sea surface dissolved oxygen for the World Ocean. Data from the World Ocean Atlas 2001.Oxygen is the most common component of the Earth's crust (49% by mass)[2], the second most common component of the Earth as a whole (28.2% by mass), and the second most common component of the Earth's atmosphere (20.947% by volume).

See also Silicate minerals, Oxide minerals.


[edit]
Compounds
Dioxygen, O2, is a gas and consists of 2 oxygen atoms. Oxygen is most commonly encountered in this form, as it makes up 21% of the atmosphere. Ozone, O3, is a gas and consists of 3 oxygen atomsDue to its electronegativity, oxygen forms chemical bonds with almost all other elements hence the origin of the original definition of oxidation. The only elements to escape the possibility of oxidation are a few of the noble gases. The most famous of these oxides is water (H2O). Other well known examples include compounds of carbon and oxygen, such as carbon dioxide (CO2), alcohols (R-OH), carbonyls, (R-CO-H( or R2)), and carboxylic acids (R-COOH). Oxygenated radicals such as chlorates (ClO3−), perchlorates (ClO4−), chromates (CrO42−), dichromates (Cr2O72−), permanganates (MnO4−), and nitrates (NO3−) are strong oxidizing agents in and of themselves. Many metals such as iron bond with oxygen atoms, iron (III) oxide (Fe2O3). Ozone (O3) is formed by electrostatic discharge in the presence of molecular oxygen. A double oxygen molecule (O2)2 is known and is found as a minor component of liquid oxygen. Epoxides are ethers in which the oxygen atom is part of a ring of three atoms.

One unexpected oxygen compound is dioxygen hexafluoroplatinate O2+PtF6−. It was discovered when Neil Bartlett was studying the properties of PtF6. He noticed a change in color when this compound was exposed to atmospheric air. Bartlett reasoned that xenon should also be oxidized by PtF6. This led him to the discovery of xenon hexafluoroplatinate Xe+PtF6−.

See also Oxygen compounds.

[edit]
Isotopes
Main article: isotopes of oxygen
Oxygen has seventeen known isotopes with atomic masses ranging from 12.03 u to 28.06 u. Three are stable, 16O, 17O, and 18O, of which 16O is the most abundant (over 99.7%). The radioisotopes all have half-lives of less than three minutes.

An atomic weight of 16 was assigned to oxygen prior to the definition of the unified atomic mass unit based upon 12C. Since physicists referred to 16O only, while chemists meant the naturally abundant mixture of isotopes, this led to slightly different atomic weight scales.

[edit]
Precautions
Oxygen can be toxic at elevated partial pressures (i.e. high relative concentrations). This is important in deep scuba diving and surface supplied diving and when using equipment which can provide high concentrations of oxygen such as rebreathers.

Certain derivatives of oxygen, such as ozone (O3), singlet oxygen, hydrogen peroxide, hydroxyl radicals and superoxide, are also highly toxic. The body has developed mechanisms to protect against these toxic compounds. For instance, the naturally-occurring glutathione can act as an antioxidant, as can bilirubin which is normally a breakdown product of hemoglobin. To protect against the destructive nature of peroxides, nearly every organism on earth has developed some form of the enzyme catalase, which very quickly disproportionates peroxide into water and dioxygen.

Highly concentrated sources of oxygen promote rapid combustion and therefore are fire and explosion hazards in the presence of fuels. The fire that killed the Apollo 1 crew on a test launchpad spread so rapidly because the capsule was pressurized with pure oxygen as would be usual in an actual flight, but to maintain positive pressure in the capsule, this was at slightly more than atmospheric pressure instead of the 1/3 pressure that would be used in flight. (See partial pressure.) Similar hazards also apply to compounds of oxygen with a high oxidative potential, such as chlorates, perchlorates, and dichromates; they also can often cause chemical burns.

Oxygen derivatives are prone to form free radicals, especially in metabolic processes. Because they can cause severe damage to cells and their DNA, they form part of theories of carcinogenesis and aging.







Mercury 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)
Critical point 1750 K, 172.00 MPa
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 Latinized 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 standard room temperature (the others are the metals caesium, francium, and gallium, and the nonmetal bromine). Mercury is used in dental amalgam as well as thermometers, barometers and other scientific apparatus, 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) due to concerns about the element's toxicity. Mercury is mostly obtained by reduction from the mineral cinnabar.

Contents [hide]
1 Applications
2 History
2.1 Dentistry
2.2 Medicine
3 Mineral occurrence
4 Compounds
5 Isotopes
6 Occurrence in the environment
7 Health and Environmental Effects
8 Precautions and regulation
8.1 Occupational exposure
8.2 Mercury in fish
8.3 Release of mercury into the environment
8.4 Mercury and aluminium
9 Trivia
10 References
10.1 History
11 External links



[edit]
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 (In the United States, non-prescription sale of mercury fever thermometers was banned by a number of different states and localities). Other uses:

Mercury sphygmomanometers.
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.
Liquid mercury was sometimes used as a coolant for nuclear reactors. However sodium is proposed for reactors cooled with liquid metal, because the high density of mercury requires much energy for circulating the coolant.
Mercury was once used in the amalgamation process of refining gold and silver ores. This polluting practice is still used 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. It must be emphasized that the former two procedures, especially, are extremely hazardous.
Alexander Calder built a mercury fountain for the Spanish Pavilion at the 1937 World's Fair in Paris.
Used in electrochemistry as part of a secondary reference electrode called the calomel electrode as an alternative to the Standard Hydrogen Electrode. This is used to work out the electrode potential of half cells.
Miscellaneous uses: mercury switches, electrodes in some types of electrolysis, batteries (mercury cells, including for sodium hydroxide and chlorine production, and alkaline batteries), catalysts, insecticides, dental amalgams/preparations and liquid mirror telescopes.

Thiomersal, an organic compound used as a preservative in vaccines and tattoo inks and vanishingly (in vaccines) (See also Thiomersal controversy.
Historical uses: preserving wood, developing daguerreotypes, silvering mirrors, anti-fouling paints (discontinued in 1990), herbicides (discontinued in 1995), 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 to bare aluminium, causing the metal to rapidly corrode. This would cause mysterious structural failures.

In Islamic Spain it was used for filling decorative pools and for fountains [1] [2].

In some applications, mercury can be replaced with less toxic but considerably more expensive galinstan alloy.

A new atomic clock is being made using mercury instead of caesium. It will be accurate up to 10 billion years.

[edit]
History
Mercury was known to the ancient Chinese and Hindus and was found in Egyptian tombs that date from 1500 BC. In China, India and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health. China's first emperor, Qin Shihuang Di, is said to have been buried in a tomb that contained rivers of flowing mercury, representative of the rivers of China. The ancient Greeks used mercury in ointments and the Romans used it in cosmetics. By 500 BC mercury was used to make amalgams with other metals. The Indian word for alchemy is Rasavātam 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 phrase "mad as a hatter"; see the hatter article on the origin of the phrase.

[edit]
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 mercury 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." This position is not shared by all governments and there is an ongoing dental amalgam controversy.

[edit]
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). Many people believe that this mercury-based preservative can trigger autism in children who are already genetically predisposed to it[1], however the medical evidence is inconclusive, and does not seem to show a risk to the child greater than that resulting from missing vaccines. 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). Mercury compounds are found in some over-the-counter drugs, 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).

In the European Union, RoHS legislation being introduced will ban mercury from certain products, and limit the amount of mercury in other products to less than 1000 ppm (except for certain exemptions).

[edit]
Mineral occurrence
Mercury oreMercury is an extremely rare element in the earth's crust, having an average crustal abundance by mass of only 0.08 parts per million. However, because it does not blend geochemically with those elements that comprise the majority of the crustal mass, mercury ores can be extraordinarily concentrated considering the element's abundance in ordinary rock. The richest mercury ores contain up to 2.5% mercury by mass, and even the leanest concentrated deposits are at least 0.1% mercury (12,000 times average crustal abundance). This makes mercury ore the most easily depleted of all metal ores. Depletion of mercury ores have been a major concern since the 1960s and it is now almost certain that the last mineable deposits were discovered in Algeria in the mid-1970s. Since the early 1970s, total world production of mercury has fallen from 9,000 tonnes to 1,600 tonnes due to depletion of reserves.

It is found either as a native metal (rare) or in cinnabar, corderoite, livingstonite, and other minerals with cinnabar (HgS) being the most common ore. Most present-day production occurs in Spain, Kyrgyzstan, China and Tajikistan. Over 100,000 tons of mercury were mined from the region of Huancavelica, Peru, over the course of three centuries following the discovery of deposits there in 1563; mercury from Huancavelica was crucial in the production of silver in colonial Spanish America. Many former ores in Italy, Slovenia, the United States and Mexico which once produced a large proportion of the world's supply have now been completely mined out. The metal is extracted by heating cinnabar in a current of air and condensing the vapor. The equation for this extraction is

HgS + O2 → Hg + SO2
See also Category:Mercury minerals, Category:Mercury mines.

[edit]
Compounds
The most important salts are:

Mercury(I) chloride (AKA calomel) is sometimes still used in medicine and acousto-optical filters
Mercury(II) chloride (which is very corrosive, sublimates and is a violent poison)
Mercury fulminate, (a detonator widely used in explosives),
Mercury(II) sulfide (AKA cinnabar mercuric ore still used in oriental medicine, or vermilion which is a high-grade paint pigment),
Mercury(II) selenide a semi-metal,
Mercury(II) telluride a semi-metal, and
Mercury cadmium telluride and mercury zinc telluride, infrared detector materials.
Laboratory tests have found that an electrical discharge causes the noble gases to combine with mercury vapor. These compounds are held together with van der Waals forces and result in HgNe, HgAr, HgKr, and HgXe. Organic mercury compounds are also important. Methylmercury is a dangerous compound that is widely found as a pollutant in water bodies and streams.

See also Category:Mercury compounds.

[edit]
Isotopes
There are seven stable isotopes of mercury with Hg-202 being the most abundant (29.86%). The longest-lived radioisotopes are Hg-194 with a half-life of 444 years, and Hg-203 with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lifes that are less than a day.

[edit]
Occurrence in the environment
Amount of atmospheric mercury deposited at Fremont glacier over the last 270 years.Abundance

Crustal ~7×10-2 mg/kg
Oceans ~3×10-5 mg/l
Preindustrial deposition rates of mercury from the atmosphere may be in the range of 4 ng/L in the western USA. Although that can be considered a natural level of exposure, regional or global sources have significant effects. Volcanic eruptions can increase the atmospheric source by 4–6 times. [3]

Mercury enters the environment as a pollutant from various industries:

coal-fired power plants are the largest source (40% of USA emissions in 1999). [4]
industrial processes
chlorine, steel, phosphate & gold production
metal smelting
manufacture & repair of weather and electronic devices
incineration of municipal waste streams
medical applications, including vaccinations
dentistry
cosmetic industries
laboratory work involving mercury or sulfur compounds
Mercury also enters into the environment through the disposal (e.g., landfilling, incineration) of certain products. Products containing mercury include: auto parts, batteries, fluorescent bulbs, medical products, thermometers, and thermostats.[5] Due to health concerns (see below), toxics use reduction efforts are cutting back or eliminating mercury in such products. For example, most thermometers now use pigmented alcohol instead of mercury. Mercury thermometers are still occasionally used in the medical field because they are more accurate than alcohol thermometers, though both are being replaced by electronic thermometers. Mercury thermometers are still widely used for certain scientific applications because of their greater accuracy and working range.

One of the worst industrial disasters in history was caused by the dumping of mercury compounds into Minamata Bay, Japan. The Chisso Corporation, a fertilizer and later petrochemical company, was found responsible for polluting the bay from 1932–1968. It is estimated that over 3,000 people suffered various deformities, severe mercury poisoning symptoms or death from what became known as Minamata disease.

[edit]
Health and Environmental Effects
See mercury poisoning

[edit]
Precautions and regulation
Mercury should be handled with care. Containers of mercury should be securely sealed to avoid spills and evaporation. Heating of mercury, or compounds of mercury that may decompose when heated, should always be carried out with adequate ventilation in order to avoid human exposure to mercury vapor.

[edit]
Occupational exposure
Due to the health effects of mercury exposure, industrial and commercial uses are regulated in many countries. The World Health Organization, OSHA, and NIOSH all treat mercury as an occupational hazard, and have established specific occupational exposure limits. Environmental releases and disposal of mercury are regulated in the U.S. primarily by the Environmental Protection Agency.

[edit]
Mercury in fish
Fish and shellfish have a natural tendency to concentrate mercury in their bodies, often in the form of methylmercury, a highly toxic organic compound of mercury. Species of fish that are high on the food chain, such as shark, swordfish, king mackerel, albacore tuna, and tilefish contain higher concentrations of mercury than others. This is because mercury is stored in the muscle tissues of fish, and when a predatory fish eats another fish, it assumes the entire body burden of mercury in the consumed fish. Since fish are less efficient at depurating than accumulating methylmercury, fish-tissue concentrations increase over time. Thus species that are high on the food chain amass body burdens of mercury that can be ten times higher, or more, than the species they consume. This process is called biomagnification. The complexities associated with mercury fate and transport are relatively succinctly described by USEPA in their 1997 Mercury Study Report to Congress. Because methylmercury and high levels of elemental mercury can be particularly toxic to unborn or young children, organizations such as the U.S. EPA and FDA recommend that women who are pregnant or plan to become pregnant within the next one or two years, as well as young children avoid eating more than 6 ounces (one average meal) per week. In the United States the FDA has an action level for methyl mercury in commercial marine and freshwater fish that is 1.0 parts per million (ppm), and in Canada the limit for the total of mercury content is 0.5 (ppm) [1,2].

Species with characteristically low levels of mercury include shrimp, tilapia, salmon, pollock, and catfish (FDA March 2004). The FDA characterizes shrimp, catfish, pollock, salmon, and canned light tuna as low-mercury seafood, although recent tests have indicated that up to 6 percent of canned light tuna may contain high levels. (Chicago Tribune)

The effects of consuming fish high in mercury is in dispute with the University of Rochester's study of people in the Republic of the Seychelles. While there is no doubt high level exposure to methyl mercury is definitely toxic, low level exposure isn't. ([6])

[edit]
Release of mercury into the environment
The environmental consideration of mercury use in a particular product can sometimes be complicated. For instance compact fluorescent light bulbs, which use a very small amount of mercury (in 2004 two-thirds of CFL lamps sold contained 5 mg Hg or less per bulb, while 96 percent contained 10 mg or less), due to their far higher efficiency over incandescent bulbs actually emit less mercury to the environment when they are powered using energy from a coal power plant. Mercury use of compact fluorescent bulb vs. incandescent bulb when powered by electricity generated from coal.The primary sources of mercury to the environment are fossil fuel burning (primarily coal) and solid waste incineration (Nriagu & Pacyna, 1988).

The United States Clean Air Act, passed in 1990, put mercury on a list of toxic pollutants which need to be controlled to the greatest possible extent. Thus, certain industries that emit mercury into the environment must install maximum achievable control technologies (MACT). However, a March 2005 EPA rule[7] took power plants off the list of sources which must reduce mercury to the maximum extent. Instead, a cap and trade rule was issued, with most of the reductions in mercury pollution from power plants beginning in the year 2018. The rule was being subjected to legal challenges from several states in 2005.

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Mercury and aluminium
Mercury readily combines with aluminium to form an amalgam when the two pure metals come into contact. However, when the amalgam is exposed to air, the aluminium oxidizes, leaving behind mercury. The oxide flakes away, exposing more mercury amalgam, which repeats the process. This process continues until the supply of amalgam is exhausted, and since it releases mercury, a small amount of mercury can “eat through” a large amount of aluminium over time, by progressively forming amalgam and relinquishing the aluminium as oxide.

Aluminium in air is ordinarily protected by a molecule-thin layer of its own oxide (which is not porous to oxygen). Mercury coming into contact with this oxide does no harm. However, if any elemental aluminium is exposed (even by a recent scratch), the mercury may combine with it, starting the process described above, and potentially damaging a large part of the aluminium before it finally ends (Ornitz 1998).

For this reason, restrictions are placed on the use and handling of mercury in proximity with aluminium. In particular, mercury is not allowed aboard aircraft under most circumstances because of the risk of it forming amalgam with exposed aluminium parts in the aircraft.