{"id":365,"date":"2020-04-09T11:18:19","date_gmt":"2020-04-09T11:18:19","guid":{"rendered":"https:\/\/thechemicalelements.com\/?page_id=365"},"modified":"2023-08-15T10:22:32","modified_gmt":"2023-08-15T10:22:32","slug":"selenium","status":"publish","type":"post","link":"https:\/\/thechemicalelements.com\/selenium\/","title":{"rendered":"Selenium (Se)"},"content":{"rendered":"\n

Selenium is a chemical element with the atomic number 34 in the periodic table. It occurs naturally in Earth\u2019s crust, especially in carbonate rocks and volcanic and sedimentary soils. Being a member of the sulphur group of periodic table elements, this chalcogen has six electrons in the outermost shell and valences of -2, 4, and 6. <\/span><\/p>\n\n\n\n

As one of the essential trace minerals, selenium participates in numerous vital processes in the human body. On the other hand, high accumulations of this substance in bodily tissues and organs may lead to adverse health effects.\u00a0<\/span><\/p>\n\n\n\n

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Chemical and Physical Properties of Selenium<\/span><\/h3>\n\n\n\n
Property<\/td>Value<\/td><\/tr>
Symbol of Selenium<\/td>Se<\/td><\/tr>
Name<\/td>Selenium<\/td><\/tr>
Atomic Number of Selenium<\/td>34<\/td><\/tr>
Group of Selenium<\/td>Non-Metal<\/td><\/tr>
Crystal Structure of Selenium<\/td>Hexagonal<\/td><\/tr>
Atomic Weight of Selenium<\/td>78.96<\/td><\/tr>
Shells of Selenium<\/td>2,8,18,6<\/td><\/tr>
Orbitals of Selenium<\/td>[Ar] 3d10 4s2 4p4<\/td><\/tr>
Valence of Selenium<\/td>-2,4,6<\/td><\/tr>
Electronegativity according to Pauling<\/td>2.55<\/td><\/tr>
Covalent Radius of Selenium<\/td>1.16 \u00c5<\/td><\/tr>
Ionic Radius of Selenium<\/td>.50 (+4) \u00c5<\/td><\/tr>
Atomic Radius of Selenium<\/td>1.22 \u00c5<\/td><\/tr>
Atomic Volume of Selenium<\/td>16.45 cm\u00b3\/mol<\/td><\/tr>
Name Origin of Selenium<\/td>Greek: sel\u00ean\u00ea (moon).<\/td><\/tr>
Discovered By<\/td>J\u00f6ns Jacob Berzelius<\/td><\/tr>
Year<\/td>1818<\/td><\/tr>
Location<\/td>Sweden<\/td><\/tr>
Pronounced of Selenium<\/td>si-LEE-ni-em<\/td><\/tr>
Oxydation States of Selenium<\/td>-2,(4),6<\/td><\/tr>
Density of Selenium<\/td>4.79 g\/cm\u00b3<\/td><\/tr>
Uses of Selenium<\/td>Light causes it to conduct electricity more easily. It is used in photoelectric cells, TV cameras, xerography machines and as a semiconductor in solar batteries and rectifiers. Also colors glass red.<\/td><\/tr>
Description of Selenium<\/td>Redish-brown liquid.<\/td><\/tr>
Physical state<\/td>Solid (non-metal) substance at room temperature<\/td><\/tr>
Half-life<\/td>From less than 50 milliseconds to 0.97(5)\u00d71020 years<\/td><\/tr>
Isotopes<\/td>30<\/td><\/tr>
Most characteristic isotope<\/td>80Se<\/td><\/tr>
The energy of the first ionization<\/td>940.7 kJ.mol-1<\/td><\/tr>
The energy of the second ionization<\/td>2045 kJ.mol-1<\/td><\/tr>
The energy of the third ionization<\/td>2973.7 kJ.mol-1<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

With the periodic table symbol Se, atomic number 34, atomic mass of 78.96 g.mol<\/span>-1<\/span>, and electron configuration [Ar] 3d<\/span>10<\/span>4s<\/span>2<\/span>4p<\/span>4<\/span>, actinium<\/a> is ductile and reaches its boiling point at 685\u00b0C, 1265\u00b0F, 958 K, while the melting point is achieved at 220.8\u00b0C, 429.4\u00b0F, 494 K. This member of the sulfur<\/a> family of elements in the periodic table has an electronegativity of 2.4 according to Pauling, whereas the atomic radius according to van der Waals is 0.14 nm. <\/span><\/p>\n\n\n\n

Classified under the element sulfur in Group 16 of the periodic table, selenium resembles the chemical properties of this group of chemicals. A member of the chalcogen family of elements, this metalloid displays both a and a photoconductive action (electrical resistance decreases with increased illumination), and a photovoltaic action (converts light to electricity).    <\/span><\/p>\n\n\n\n

This chemical occurs in a form of several different allotropes. The crystalline hexagonal selenium is the most stable form with a metallic gray appearance. Crystalline monoclinic selenium occurs in a deep red color, while the amorphous selenium has is red in the powder form, but occurs as black in its vitreous form.<\/span><\/p>\n\n\n\n

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How Was Selenium Discovered?<\/span><\/h2>\n\n\n\n

In 1817, the distinguished Swedish chemist Jacob Berzelius (1779 – 1848) discovered selenium as an impurity in sulphuric acid. While studying the technical issues related to the production of sulfuric acid and nitric acid (aqua fortis), this accomplished experimenter\u2019s curiosity was directed toward a reddish sludge obtained from a Falun pyrite sample.<\/span><\/p>\n\n\n\n

Together with Johan Gottlieb Gahn (1745 – 1818), Berzelius exposed over 200 kg of sulfur to obtain nearly 3 grams of its precipitate. The analysis of the result from this experiment pointed out a presence of tellurium<\/a> in the substance. But, familiar with the fact that this chemical element has never been traced in the minerals mined near Falun (a city in Sweden), Berzelius continued to experiment with the sludge. <\/span><\/p>\n\n\n\n

In the new round of chemical analysis, Jacob Berzelius observed similarities of the substance in front of him with sulphur, but some metallic properties too. That new substance was selenium.\u00a0<\/span><\/p>\n\n\n\n

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How Did Selenium Get Its Name?<\/span><\/h2>\n\n\n\n

Upon observing the striking resemblance of the chemical properties between <\/span>tellurium<\/span><\/i> (named after the Greek word for \u201cearth\u201d), Berzelius named his newly discovered chemical element <\/a><\/span>selenium<\/span><\/i> after the Greek word “selene”, meaning “moon”. Selene is also considered to be a Greek goddess of the moon.\u00a0<\/span><\/p>\n\n\n\n

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Where Can You Find Selenium?<\/span><\/h2>\n\n\n\n

In Earth’s crust, selenium commonly occurs as selenite, selenate, and selenides found in sulfide minerals, copper<\/a> ores, and rare minerals (such as clausthalite, crooksite, and eucairite). The amino acids selenocysteine, methylselenocysteine, and selenomethionine also contain selenium as one of the key components of their structure. Selenium can be found in the soil (with different degrees of concentration) and ocean waters, as well. <\/span><\/p>\n\n\n\n

Smelting, extraction of sulfide ores, as well as coal burning also releases selenium. In its pure, elemental form, selenium can be obtained from the slimes and sludges formed during the production of sulfuric acid. <\/span><\/p>\n\n\n\n

For commercial purposes, this substance is obtained as a byproduct of electrolytic copper refining. Germany, United States, Japan, Belgium, Bolivia, and Russia are the leading countries in the world regarding the selenium refinement process.\u00a0<\/span><\/p>\n\n\n\n

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Selenide Minerals<\/span><\/h3>\n\n\n\n

The following list presents the minerals in which selenium can also be found:\u00a0<\/span><\/p>\n\n\n\n