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Chalcogenides
: 220px, Cadmium sulfide, a prototypical metal chalcogenide, is used as a yellow pigment. A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term chalcogenide is more commonly reserved for sulfides, selenides, tellurides, and polonides, rather than oxides. Many metal ores exist as chalcogenides. Photoconductive chalcogenide glasses are used in xerography. Some pigments and catalysts are also based on chalcogenides. The metal dichalcogenide MoS2 is a common solid lubricant. Alkali metal and alkaline earth chalcogenides Alkali metal and alkaline earth monochalcogenides are salt-like, being colourless and often water-soluble. The sulfides tend to undergo hydrolysis to form derivatives containing bisulfide (SH−) anions. The alkali metal chalcogenides often crystallize with the antifluorite structure and the alkaline eart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chalcogen
The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive elements polonium (Po) and livermorium (Lv). Often, oxygen is treated separately from the other chalcogens, sometimes even excluded from the scope of the term "chalcogen" altogether, due to its very different chemical behavior from sulfur, selenium, tellurium, and polonium. The word "chalcogen" is derived from a combination of the Greek word () principally meaning copper (the term was also used for bronze, brass, any metal in the poetic sense, ore and coin), and the Latinized Greek word , meaning ''born'' or ''produced''. Sulfur has been known since antiquity, and oxygen was recognized as an element in the 18th century. Selenium, tellurium and polonium were discovered in the 19th century, and livermorium in 2000. All of the ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Group 16 Element
The chalcogens (ore forming) ( ) are the chemical elements in group (periodic table), group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the Radioactive decay, radioactive elements polonium (Po) and livermorium (Lv). Often, oxygen is treated separately from the other chalcogens, sometimes even excluded from the scope of the term "chalcogen" altogether, due to its very different chemical behavior from sulfur, selenium, tellurium, and polonium. The word "chalcogen" is derived from a combination of the Greek word () principally meaning copper (the term was also used for bronze, brass, any metal in the poetic sense, ore and coin), and the Latinized Greek word , meaning ''born'' or ''produced''. Sulfur has been known since antiquity, and oxygen was recognized as an element in the 18th century. Selenium, tellurium and polonium were discovered in the 19th century, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chalcogenide Glass
Chalcogenide glass (pronounced hard ''ch'' as in ''chemistry'') is a glass containing one or more heavy chalcogens (sulfur, selenium or tellurium; polonium is also a heavy chalcogen but too radioactive to use). Chalcogenide materials behave rather differently from oxides, in particular their lower band gaps contribute to very dissimilar optical and electrical properties. The classical chalcogenide glasses (mainly sulfur-based ones such as As-S or Ge-S) are strong glass-formers and possess glasses within large concentration regions. Glass-forming abilities decrease with increasing molar weight of constituent elements; i.e., S > Se > Te. Chalcogenide compounds such as AgInSbTe and GeSbTe are used in rewritable optical disks and phase-change memory devices. They are fragile glass-formers: by controlling heating and annealing (cooling), they can be switched between an amorphous (glassy) and a crystalline state, thereby changing their optical and electrical properties and allowing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molybdenum Disulfide
Molybdenum disulfide (or moly) is an inorganic chemistry, inorganic compound composed of molybdenum and sulfur. Its chemical formula is . The compound is classified as a transition metal dichalcogenide. It is a silvery black solid that occurs as the mineral molybdenite, the principal ore for molybdenum.Sebenik, Roger F. ''et al''. (2005) "Molybdenum and Molybdenum Compounds", ''Ullmann's Encyclopedia of Chemical Technology''. Wiley-VCH, Weinheim. is relatively unreactive. It is unaffected by dilute acids and oxygen. In appearance and feel, molybdenum disulfide is similar to graphite. It is widely used as a dry lubricant because of its low friction and robustness. Bulk is a Diamagnetism, diamagnetic, indirect bandgap semiconductor similar to silicon, with a bandgap of 1.23 eV. Production is naturally found as either molybdenite, a crystalline mineral, or jordisite, a rare low temperature form of molybdenite. Molybdenite ore is processed by Froth flotation, flotation to give ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superconductivity
Superconductivity is a set of physical properties observed in superconductors: materials where Electrical resistance and conductance, electrical resistance vanishes and Magnetic field, magnetic fields are expelled from the material. Unlike an ordinary metallic Electrical conductor, conductor, whose resistance decreases gradually as its temperature is lowered, even down to near absolute zero, a superconductor has a characteristic Phase transition, critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source. The superconductivity phenomenon was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. Like ferromagnetism and Atomic spectral line, atomic spectral lines, superconductivity is a phenomenon which can only be explained by quantum mechanics. It is characterized by the Meissner effect, the complete cancellation of the magnetic field in the interior of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Chloride
Sodium chloride , commonly known as Salt#Edible salt, edible salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic, and occurs as the mineral halite. In its edible form, it is commonly used as a condiment and curing (food preservation), food preservative. Large quantities of sodium chloride are used in many industrial processes, and it is a major source of sodium and chlorine compounds used as feedstocks for further Chemical synthesis, chemical syntheses. Another major application of sodium chloride is deicing of roadways in sub-freezing weather. Uses In addition to the many familiar domestic uses of salt, more dominant applications of the approximately 250 million tonnes per year production (2008 data) include chemicals and de-icing.Westphal, Gisbert ''et al.'' (2002) "Sodium Chloride" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim . Chem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pigment
A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored substances which are soluble or go into solution at some stage in their use. Dyes are often organic compounds whereas pigments are often inorganic compound, inorganic. Pigments of prehistoric and historic value include ochre, charcoal, and lapis lazuli. Economic impact In 2006, around 7.4 million tons of inorganic chemistry, inorganic, organic chemistry, organic, and special pigments were marketed worldwide. According to an April 2018 report by ''Bloomberg Businessweek'', the estimated value of the pigment industry globally is $30 billion. The value of titanium dioxide – used to enhance the white brightness of many products – was placed at $13.2 billion per year, while the color Ferrari red is valued at $300 million each yea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nonstoichiometry
Non-stoichiometric compounds are chemical compounds, almost always solid inorganic compounds, having elemental composition whose proportions cannot be represented by a ratio of small natural numbers (i.e. an empirical formula); most often, in such materials, some small percentage of atoms are missing or too many atoms are packed into an otherwise perfect lattice work. Contrary to earlier definitions, modern understanding of non-stoichiometric compounds view them as homogeneous, and not mixtures of stoichiometric chemical compounds. Since the solids are overall electrically neutral, the defect is compensated by a change in the charge of other atoms in the solid, either by changing their oxidation state, or by replacing them with atoms of different elements with a different charge. Many metal oxides and sulfides have non-stoichiometric examples; for example, stoichiometric iron(II) oxide, which is rare, has the formula , whereas the more common material is nonstoichiometric, with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nickel Arsenide
Nickel arsenide is a compound of nickel and arsenic and component of the ore nickeline. It is highly toxic and a known carcinogen in humans. Uncontrolled decomposition of nickel arsenide can give rise to further toxic nickel compounds. Toxicity Nickel arsenide was one of the first compounds that revealed the toxicity of nickel. The damage to the miners' lungs was documented by Georgius Agricola in the 16th century: "kupfer-nickel" ores in the Schneeberg mines contained red-colored NiAs mineral originally mistaken for the copper ore, thus the (copper) in the name. The (demon) name was reflecting the damage it did to the health of the workers, in addition to them being unable to extract any copper from this ore. The acute oral LD50 In toxicology, the median lethal dose, LD50 (abbreviation for "lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a given substance. The value of LD50 for a substance is the dose req ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Covalent
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full valence shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonding is much more common than ionic bonding. Covalent bonding also includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, three-center two-electron bonds and three-center four-electron bonds. The term "covalence" was introduced by Irving Langmuir in 1919, with Nevil Sidgwick using "co-valent link" in the 1920s. Merriam-Webster dates the specific phrase ''covalent bond'' to 1939, recognizing its first known ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diamondoid
In chemistry, diamondoids are generalizations of the carbon cage molecule known as adamantane (C10H16), the smallest unit cage structure of the diamond crystal lattice. Diamondoids also known as nanodiamonds or condensed adamantanes may include one or more cages (adamantane, diamantane, triamantane, and higher polymantanes) as well as numerous isomeric and structural variants of adamantanes and polymantanes. These diamondoids occur naturally in petroleum deposits and have been extracted and purified into large pure crystals of polymantane molecules having more than a dozen adamantane cages per molecule. These species are of interest as molecular approximations of the diamond cubic framework, terminated with C−H bonds. Examples Examples include: * Adamantane (C10H16) * Iceane (C12H18) * BC-8 (C14H20) * Diamantane (C14H20) also ''diadamantane'', two face-fused cages * Triamantane (C18H24), also ''triadamantane''. Diamantane has four identical faces available for anchoring a n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cadmium Sulfide
Cadmium sulfide is the inorganic compound with the formula CdS. Cadmium sulfide is a yellow salt.Egon Wiberg, Arnold Frederick Holleman (2001''Inorganic Chemistry'' Elsevier It occurs in nature with two different crystal structures as the rare minerals greenockite and hawleyite, but is more prevalent as an impurity substituent in the similarly structured zinc ores sphalerite and wurtzite, which are the major economic sources of cadmium. As a compound that is easy to isolate and purify, it is the principal source of cadmium for all commercial applications. Its vivid yellow color led to its adoption as a pigment for the yellow paint "cadmium yellow" in the 1800s. Production Cadmium sulfide can be prepared by the precipitation from soluble cadmium(II) salts with sulfide ion. This reaction has been used for gravimetric analysis and qualitative inorganic analysis.The preparative route and the subsequent treatment of the product, affects the polymorphic form that is produced (i.e., c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
