Mercury (Hg), chemical element, liquid metal of Group 12 (IIb, or zinc group) of the periodic table. Atomic number 80 atomic weight 200.59 melting point −38.87 °C (−37.97 °F) boiling point 356.9 °C (674 °F) specific gravity 13.5 at 20 °C (68 °F) valence 1, 2 electron configuration 2-8-18-32-18-2. The atomic number of an element is equal to the total number of protons in the nucleus of the atoms of that element. The atomic number can provide insight into the electronic configuration of the element. For example, carbon has an electron configuration of He 2s 2 2p 2, since its atomic number is 6. Mercury Properties. Mercury is a Block D, Group 12, Period 6 element. The number of electrons in each of Mercury's shells is 2, 8, 18,32, 18, 2 and its electronic configuration is Xe 4f 14 5d 10 6s 2. Atomic number (number of protons in the nucleus): 80; Atomic symbol (on the Periodic Table of Elements): Hg; Atomic weight (average mass of the atom): 200.59.
Mercury is a chemical element with symbol Hg and atomic number 80. It is commonly known as quicksilver and was formerly named hydrargyrum
Discovery and History
Mercury can be rightly considered as one of the elements with most ancient existence, and its discovery dates back to around 1500 B.C [1]. Initially, it was referred to as the water-silver or the liquid -silver (originated from the Greek term hydro-argyros used by Aristotle) and later Romans changed its name to Hydragyrum. In the 6th century, alchemists changed its name after the fast-moving Roman god, Mercury, with the symbol Hg (from its initial name Hydro-argyros). Mercury was greatly popular, especially in Chinese traditional medicine, due to its unique solid-liquid nature [2]. The metallic properties of mercury were discovered by Adam Braun and Mikhail Lomonosov (1759), who successfully froze a mercury thermometer.
Mercury
Periodic Table Classification | Group 12 Period 6 |
---|---|
State at 20C | Liquid |
Color | Silvery |
Electron Configuration | [Xe] 4f14 5d10 6s2 |
Electron Number | 80 |
Proton Number | 80 |
Electron Shell | 2, 8, 18, 32, 18, 2 |
Density | 13.55 g.cm-3 at 20°C |
Atomic number | 80 |
Atomic Mass | 200.59 g.mol -1 |
Electronegativity according to Pauling | 2.00 |
Occurrence
The occurrence of mercury is not very common. It is present in crust of the Earth on an average of 0.08 gram, making 0.003 ounce per ton of the rock. Mercury is rarely present in free, pure form and its principally present in the form of the red sulfide, termed as cinnabar (HgS). Naturally, mercury is present near hot springs and volcanoes in isolated drops or in larger fluid masses. Eruption of volcanoes can lead to 4-6 times increase in the atmospheric presence of volcanoes [3]. Around 2/3rd of supply of mercury in the world comes from China, and Chile and Kyrgyzstan make up the rest [4]. Mercury is often obtained as a by-product during the process of gold mining. Some other natural alloys of mercury have also been found, including potarite (with palladium) gold amalgam and moschellandsbergite (with silver), but these are extremely rare.
Physical characteristics
Mercury is a silver-white dense metal with a mirror like appearance. And have the unique characteristic of being liquid at room temperature. Mercury have boiling and melting points of 356.9 C and -38.87, respectively. It has atomic number of 80 and a molecular weight of 200.59 and belong to the Group 12 (Zinc group, II b) of the periodic table [2].
Chemical characteristics
Mercury is highly poisonous. It is generally stable in dry environment but exposure to water lead to the production of gray oxide coating on its surface. It has a low solubility for gases as compared to water. Mercury can vaporize and can stay in the atmosphere for many months.
Salts of Mercury
Various salts of mercury are present that have distinct characteristics and significances. These include mercury (I) chloride (used in medicine), Mercury (II) chloride (a very corrosive and poisonous substance);); Mercury (II) oxide (main oxide of mercury); Mercury fulminate (a detonator used in explosives widely; Mercury (II) selenide; Mercury (II) sulfide (found naturally as the ore cinnabar which is widely used paint pigment); Mercury (II) telluride, and Mercury zinc telluride (used in semiconductors) [2].
Significance and Uses
Despites its toxicity, mercury have found wide usage in variety of industries. Some of the main uses of mercury are described below:
- Good electrical conductivity [5]
Used in making electrical switches
- Low thermal conductivity with high thermal neutron capture [5]
Used as shield and coolant in nuclear reactors
- Health care and dentistry [5]
Main use in production of dental amalgam, B.P apparatus (sphygmomanometers), and thermometers.
- Agricultural industries
Used in making fungicides
- Electricity generation
Due to higher boiling point as compared to water, vapors of mercury are being used instead of steam in electrical generating plants.
Atomic Number Of Hg
- Cosmetic industry
Making mascaras
- Mercury is used in mercury-vapor lamps (which emit light with UV radiation), and are used in street lights, UV lights and sun lamps.
- Mercury is used the production of caustic soda (sodium hydroxide) and chlorine.
Health hazards
Toxicity of mercury is primarily caused by inhalation of the vapors, followed by ingestion of soluble compounds, or dermal absorption of mercury. Once released into the air, mercury gets widely dispersed and remain accumulated in the environment. Ultimately, it finds it way to the bottom of water bodies, and is transformed into methyl mercury, which is the more toxic organic form. Traces of methyl mercury contamination have been reported in fish tissues [6].
Isotopes of Mercury
Mercury (hg) Atomic Number
There are 34 isotopes of mercury (mass number from 175-208). In natural form, mercury is a mixture of seven stable isotopes: 196Hg (0.15 percent), 198Hg (9.97 percent), 199Hg (16.87 percent), 200Hg (23.10 percent), 201Hg (13.18 percent), 202Hg (29.86 percent), and 204Hg (6.87 percent).
REFERENCES
[1] Mary Elvira Weeks, The discovery of the elements. II. Elements known to the alchemists., J. Chem. Educ., 1932, 9 (1), p11
[2]. Rustagi, N., & Singh, R. (2010). Mercury and health care. Indian Journal of Occupational and Environmental Medicine, 14(2), 45–48. http://doi.org/10.4103/0019-5278.72240
[3]. Glacial Ice Cores Reveal A Record of Natural and Anthropogenic Atmospheric Mercury Deposition for the Last 270 Years. United States Geological Survey (USGS) Science for a changing world.
[4]. Brown TJ, Hetherington LE, Hannis SD, Bide T, Benham AJ, Idoine NE, et al. 1st ed. Keyworth, Nottigham: Natural Environment Research Council; 2009. World Mineral Production 2003-07.British Geological Survey
[5] Hammond CR. 81st ed. Cleveland, Ohio: CRC press; 2000. Elements, in Handbook of Chemistry and Physics. Available from: http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/elements.pdf [last accessed on 2010 Apr 8] [Ref list]
[6] National Research Council. Toxicological effects of methylmercury. U.S: National Academies Press; 2000. Board on Environmental Studies and Toxicology. [Ref list]
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In the modern periodic table, the elements are listed in order of increasing atomic number. The atomic number is the number of protons in the nucleus of an atom. The number of protons define the identity of an element (i.e., an element with 6 protons is a carbon atom, no matter how many neutrons may be present). The number of protons determines how many electrons surround the nucleus, and it is the arrangement of these electrons that determines most of the chemical behavior of an element.
In a periodic table arranged in order of increasing atomic number, elements having similar chemical properties naturally line up in the same column (group). For instance, all of the elements in Group 1A are relatively soft metals, react violently with water, and form 1+ charges; all of the elements in Group 8A are unreactive, monatomic gases at room temperature, etc. In other words, there is a periodic repetition of the properties of the chemical elements with increasing mass.
In the original periodic table published by Dimitri Mendeleev in 1869, the elements were arranged according to increasing atomic mass— at that time, the nucleus had not yet been discovered, and there was no understanding at all of the interior structure of the atom, so atomic mass was the only guide to use. Once the structure of the nucleus was understood, it became clear that it was the atomic number that governed the properties of the elements.