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                              1. ▸▸
                                • 🇬🇧 Selenium
                                • 🇨🇳 硒
                                • 🇳🇱 Selenium
                                • 🇫🇷 Sélénium
                                • 🇩🇪 Selen
                                • 🇮🇱 סלניום
                                • 🇮🇹 Selenio
                                • 🇯🇵 セレン
                                • 🇵🇹 Selênio
                                • 🇷🇺 Селен
                                • 🇪🇸 Selenio
                                • 🇸🇪 Selen

                                Selenium: the essentials

                                Selenium atoms have 34 electrons and the shell structure is 2.8.18.6. The ground state electronic configuration of neutral selenium is [Ar].3d10.4s2.4p4 and the term symbol of selenium is 3P2.

                                Selenium: description  

                                Selenium can be prepared with either an amorphous or crystalline structure. Crystalline monoclinic selenium is deep red; crystalline hexagonal selenium, the most stable variety, is a metallic grey (see picture above). Elemental selenium is relatively nontoxic and is considered to be an essential trace element. However, hydrogen selenide (H2Se) and other selenium compounds are extremely toxic, and resemble arsenic in their physiological reactions. Hydrogen selenide in a concentration of 1.5 ppm is intolerable to man. Selenium occurs in some soils in amounts sufficient to produce serious effects on animals feeding on plants such as locoweed (an American plant) grown in such soils.

                                Selenium: physical properties

                                More physical properties...

                                Selenium: heat properties

                                More thermochemical properties...

                                Selenium: atom sizes

                                More atomc size properties...

                                Selenium: electronegativities

                                More electronegativity properties...

                                Selenium: orbital properties

                                More orbital properties...

                                Selenium: abundances

                                More geological data...

                                Selenium: crystal structure

                                Se crystal structure
                                The solid state structure of selenium is: bcc (body-centred cubic).

                                More crystallographic data...

                                Selenium: biological data

                                Selenium is essential to mammals and higher plants, but only in small amounts. Selenium is said to stimulate the metabolism. It may help protest against free radical oxidants and against some heavy metals. Livestock grown in areas containing high amounts of selenium in the soil and in which a plant called Astragalus ("loco weed" in USA) is present are poisoned. This is because Astragalus concentrates selenium. On the other hand, sheep grown in areas containing deficient amounts of selenium in the soil develop "white muscle disease".

                                More biological data...

                                Selenium: uses

                                Uses...

                                Selenium: reactions

                                Reactions of selenium as the element with air, water, halogens, acids, and bases where known.

                                View reactions of selenium...

                                Selenium: binary compounds

                                Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of selenium where known.

                                View binary compounds...

                                Selenium: compound properties

                                Bond strengths; lattice energies of selenium halides, hydrides, oxides (where known); and reduction potentials where known.

                                View compound properties...

                                Selenium: history

                                Selenium was discovered by Jöns Berzelius in 1817 at Sweden. Origin of name: from the Greek word "selene" meaning "moon".

                                More history...

                                Selenium: isotopes

                                Isotope abundances of selenium
                                Isotope abundances of selenium with the most intense signal set to 100%.

                                网络斗地主下载Selenium isotopes are mainly used for the production of medical and industrial radioisotopes. Se-77 and Se-78 are used for the production of the therapeutic radioisotope Br-77. Se-80 is used for the production of the medical radioisotope Br-80m. Se-74 is used for the production of Se-75 which is used as a source in gamma radiography. Se-76 can be used for the production of the medical isotopes Br-75 and Br-76. Se-82 has been used to study double beta decay. Most of the Selenium isotopes have been used in studies into the role of Selenium as an essential nutrient.

                                More isotope and NMR data...

                                Selenium: isolation

                                Isolation: it is not usually necessary to make selenium in the laboratory as it is commercially available. While there are several selenium ores, most selenium is made as a byproduct of copper refining. It also accumulates in the residues from sulphuric acid manufacture. Extraction is complex since the method emplyed will depend upon what other compounds or elements are present. The first step usually involves an oxidation in the presence of sodium carbonate (soda ash).

                                Cu2Se + Na2CO3 + 2O2 → 2CuO + Na2SeO3 + CO2

                                The selenite Na2SeO3 is acidified with sulphuric acid. Any tellurites precipitateout leaving selenous acid, H2SeO3, in solution. Selenium is liberated from selenous acid by SO2

                                H2SeO3 + 2SO2 + H2O → Se + 2H2SO4

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