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Mercury is a chemical element with the symbol Hg and atomic number 80. It is a silver-white metal, liquid at room temperature, and has high density.

Hg is a highly toxic substance that can cause serious health problems if ingested or inhaled.

In this article, we will examine the properties, uses, and health effects of Hg in detail.



Hg has the following structure:

  • Protons: Hg has 80 protons in its nucleus, corresponding to its atomic number on the periodic table.
  • Electrons: In a neutral mercury atom, there are also 80 electrons. Electrons are distributed in various electron shells of the atom. The electron configuration of mercury can be represented, for example, as [Xe] 4f14 5d10 6s2 6p6 6d10, indicating the arrangement of electrons in different subshells.
  • Neutrons: The number of neutrons in a mercury atom can vary depending on the isotope of Hg. The most common and stable isotope of Hg has 120 neutrons. Therefore, for the stable isotope of mercury, the mass number (the sum of protons and neutrons) is approximately 200.

Valence of Mercury

The valence of Hg can vary depending on the specific chemical compound it participates in. Hg can have a valence of +1 or +2.

  • Valence +1: Mercury can form Hg²⁺ ions with a valence of +1 when it interacts with certain other elements or compounds. For example, in mercury(I) chloride (HgCl₂) or mercury(I) nitrate (Hg(NO₃)₂), mercury has a valence of +1.
  • Valence +2: In some other compounds, such as mercury(II) oxide (HgO), mercury can have a valence of +2. Valence +2 is more typical for mercury in oxide compounds.

Physical Properties

Hg is a unique element in that it is a liquid at room temperature. It has a melting point of -38.83°C and a boiling point of 356.73°C. It has a high density of 13.5 grams per cubic centimeter, making it over 13 times denser than water. It also has a low vapor pressure, meaning it evaporates slowly at room temperature.

Chemical Properties

Hg belongs to the group of transition metals and is found in Group 12 of the periodic table. It has two valence electrons and can form compounds with both +1 and +2 oxidation states. It is a relatively unreactive element that does not readily react with oxygen, water, or many other substances.


Hg has seven stable isotopes, with mercury-202 being the most common. Several radioactive isotopes of mercury, including mercury-194, mercury-197, and mercury-203, have also been identified.

Uses of Hg

  • Industrial Applications: Hg is used in various industrial processes, including the manufacture of electrical equipment, batteries, and fluorescent light bulbs. It is also used in the production of chlorine and caustic soda.
  • Medical Uses: Hg was used as a medicine for centuries, although its use has significantly declined in modern times due to its toxicity. It was once used to treat various ailments, including syphilis, but its use has been discontinued due to its toxic effects.
  • Environmental Remediation: Hg is used in the remediation of contaminated soils and waterways. It is also used in the manufacturing of environmental monitoring equipment, such as thermometers and barometers.

Health Effects of Hg

Hg is a highly toxic substance that can cause serious health problems when ingested or inhaled. Long-term exposure to Hg can lead to a range of health issues, including neurological damage, kidney damage, and respiratory problems.

  • Mercury Poisoning: Hg poisoning can occur through the consumption of contaminated food or water or through the inhalation of mercury vapors or dust. Symptoms of Hg poisoning include tremors, memory loss, irritability, and changes in vision or hearing.
  • Neurological Damage: Hg is a neurotoxin, meaning it can damage the nervous system. Prolonged exposure to Hg can lead to tremors, memory loss, and other neurological symptoms.
  • Kidney Damage: Hg can also damage the kidneys, resulting in kidney failure and other health problems related to kidney function.
  • Respiratory Issues: Inhaling Hg vapors or dust can lead to respiratory problems, including bronchitis and asthma. It can also cause lung damage and pneumonia.
  • Pregnancy and Child Development: Exposure to Hg during pregnancy can lead to developmental delays and cognitive disorders in children. It can also increase the risk of miscarriage and stillbirth.

Preventing Hg Exposure

The best way to prevent Hg exposure is to avoid consuming fish known to have high levels of mercury, such as swordfish, king mackerel, and shark, especially for pregnant women and young children. Regulatory agencies worldwide have set limits on the amount of mercury that can be present in food and the environment.

Additionally, it is important to take precautions when working with materials containing mercury in industrial settings. Protective measures, such as gloves, goggles, and respirators, should be used to prevent exposure to Hg vapor or dust.

In conclusion, Hg is a highly toxic substance that can have serious health effects when ingested or inhaled. By following safety guidelines and minimizing exposure, the risks associated with mercury can be minimized while still benefiting from its various applications in different industries.