Mercury is a chemical element symbolized by the symbol (Hg), which belongs to the elements of the twelfth group in the periodic table, known as the group of zinc, a liquid transition metal with a bright silver color, and is the only liquid metal in standard conditions of pressure and temperature. Mercury has an atomic number of 80, its atomic weight is 200.59, it’s melting point is .838.87 ° C, its boiling point is 356.9 ° C, and natural mercury is a mixture of seven different isotopes.
It was found in Egyptian tombs dating back to 1500 BC, as was known to Hindus and ancient Chinese. It was believed in China, India, and Tibet that its use leads to the healing of fractures, prolonging life, and maintaining good health in general. The Greeks mercury in ointments, as used by the Romans in cosmetics, and chemists thought it was the first material that makes up all other minerals, which can be produced by changing the amount and quality of sulfur within the mercury.
It is known in ancient Chinese and Hindus, where it was found in Egyptian tombs up to 3500 years old, note that mercury is not free in nature, but in the form of mercury sulfide compound (HgS), it should be noted that Spain and Italy produce about half of the world supply from him.
- Chemical code: Hg.
- Atomic number: 80.
- Atomic mass: 200.59.
- Group: Transition metal
- Ionization energy: 10.438 electron volts.
- Oxidation numbers: +2, +1.
Physical properties :
- Physical state: Liquid.
- Boiling point: 365.6 °.
- Freezing point: –38.85 °.
- Density: 13.59 g / cm3.
The most famous mercury compounds
It combines with many elements, forming several compounds, the most famous of which are:
- Mercury Chloride (HgCl 2 ): It is a very toxic salt.
- Hg 2 Cl 2, a disinfectant used to eliminate bacteria.
- Mercury Sulfide (HgS): Mercury sulfide is used to make red dyes.
- (HgO): Mercury oxide is used to make batteries.
Information on mercury
There is much information, including:
- It is a very rare element in the Earth’s crust, at only about 0.08 ppm, and is found mainly in mineral cinnabar, mercury sulfide that is a source of a red pigment known as cinnabar.
- It is a relatively weak conductor of heat, as most metals form excellent thermal conductors.
- It is not generally allowed on aircraft, as it easily mixes with aluminum commonly found in it, disrupting the oxide layer that keeps aluminum from oxidation and prevents corrosion.
- It has an oxidation number equal to (+4) although it often shows oxidation numbers equal (+ 1, + 2).
- It and its various compounds are highly toxic and should be handled with care. Follow special cleaning instructions when spilled to avoid exposure to toxicity. When heated.
- It reacts with oxygen in the air when heated to form mercury oxide, which then decomposes when heated at higher temperatures.
- It is located under hydrogen in the chain reaction of metals and does not react with the majority of dilute acids such as sulfuric acid.
- It forms many salts, the most important of which are: 
- Mercury (I) chloride, which is still used in medicine, and sometimes acoustic optical filters.
- Mercury (II) chloride, which is highly toxic.
- Mercury (II) oxide, the main oxide of mercury.
- Mercury (II) sulfide.
It has occupied a great place in many ancient and modern uses, including:
- It was used mainly for medical purposes, although its toxicity was discovered early.
- It has long been used to extract gold and silver from its raw materials, as it is easily dissolved in it.
- It is introduced into the manufacture of chlorine, caustic soda (sodium hydroxide) by electrolysis of saline solutions.
- Used in the preparation of agricultural and industrial pesticides, and pharmaceuticals. Included in the manufacture of ultraviolet lamps, fluorescent lamps.
- The quality of mercury electrical conductivity makes it useful for use in relays and exceptionally closed switches.
- It is used as a coolant in nuclear reactors, and in the manufacture of barometers and manometers.
- It is mainly used in many electronic and electrical applications, and in the manufacture of various chemicals.
- It is the main component of amalgam fillings in dentistry despite controversy over its health effects.
- It is part of a second electrode as an alternative to the standard hydrogen electrode in the fields of electrochemistry.
- It plays a catalytic role in some chemical reactions.
- It is included in the formation of the thiomersal organic compound, which is used as a preservative in vaccines.
- It has long been used to preserve wood, make silver mirrors, and some types of paints.
- It compounds have been used in the manufacture of antidepressants, laxatives, antipsychotics, as well as antiseptics, eye drops, nasal sprays, and some diuretics.
- Some allegations point to the use of mercury to sabotage German planes by spies.
It has a significant impact on the environment and human health, and the Clean Air Act of the United States of America, which was passed in 1990 on the list of toxic pollutants that must be controlled significantly, as one study showed that acute exposure to specific levels of between 1.1 to 44 mg / m³ (for 4-8 hours) leading to health problems such as chest pain, cough, shortness of breath, impaired lung function, pneumonia, and acute exposure to mercury vapor affects profound damage to the central nervous system, including psychotic reactions such as hallucinations, The delirium, the tendency to commit suicide, and counting A source of pollution in many different activities bugs, including the following:
- Coal-fired power plants are the main source of mercury pollution.
- Various industrial processes such as gold, steel, phosphate, chlorine, electronic hardware manufacturing, metal smelting, and other industries.
- Medical applications such as dentistry, cosmetic industries, and some vaccines.
- Gold mining within small ranges.
Mercury and pollution
Air, water, and land are both contaminated by mercury, and their sources are mercury-containing products, the largest source of which is emissions from coal-fired power plants, which are dangerous to the environment and cause serious health effects. Especially for children and pregnant women even at low rates, the EPA estimates that more than 300,000 newborns each year are at risk of increasing learning difficulties due to exposure to methylmercury.
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