transition metal

The hydrogen atom has only one electron, in the so-called s orbital, which can either be spin up () or spin down (). This orbital can be occupied by at most two electrons, one with spin up and one down (see Pauli exclusion principle). Now, consider a 1D chain of hydrogen atoms. Under band theory, we would expect the 1s orbital to form a continuous band, which would be exactly half-full. The 1-D chain of hydrogen atoms is thus predicted to be a conductor under conventional band theory. But now consider the case where the spacing between the hydrogen atoms is gradually increa ...

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Hubbard model, Hubbard model - Theory, Hubbard model - Example: 1D chain of hydrogen atoms, Hubbard model - More Complex Systems

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This is a shiny silvery, ductile metal that is corrosion resistant and chemically similar to zirconium. The properties of hafnium are markedly affected by zirconium impurities and these two elements are amongst the most difficult to separate. The only notable difference between them is their density (zirconium is about half as dense as hafnium). Hafnium carbide is the most refractory binary compound known and hafnium nitride is the most refractory of all known metal nitrides with a melting point of 3310 °C. This metal is resistant to ...

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Hafnium, Hafnium - Notable characteristics, Hafnium - Applications, Hafnium - History, Hafnium - Occurrence, Hafnium - Precautions

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Lutetium is a silvery white corrosion-resistant trivalent metal that is relatively stable in air and is the heaviest and hardest of the rare earth elements. Lutetium has the highest spin quantum number of the elements, at 7. This element is very expensive to obtain in useful quantities and therefore it has very few commercial uses. However, stable lutetium can be used as catalysts in petroleum cracking in refineries and can also b ...

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Lutetium, Lutetium - Notable characteristics and applications, Lutetium - History, Lutetium - Occurrence, Lutetium - Isotopes, Lutetium - Compounds, Lutetium - Precautions

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Rhenium is a silvery white metal, lustrous, and has one of the highest melting points of all elements, exceeded by only tungsten and carbon. It is also one of the most dense, exceeded only by platinum, iridium, and osmium. The oxidation states of rhenium include -1,+1,+2,+3,+4,+5,+6 and +7 oxidation states. The oxidation states +7,+6,+4,+2 and -1 are the most common. Its usual commercial form is a powder, but this element can be consolidated by pressing and resistance-sintering in a vacuum or hydrogen atmosphere. This procedure yields ...

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Rhenium, Rhenium - Notable characteristics, Rhenium - Applications, Rhenium - History, Rhenium - Occurrence, Rhenium - Isotopes, Rhenium - Precautions

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Ceramic - Mechanical properties. Ceramic materials are usually ionic or covalently-bonded materials, and can be crystalline or amorphous. A material held together by either type of bond will tend to fracture before any plastic deformation takes place, which results in poor toughness in these materials. Additionally, because these materials tend to be porous, the pores and other microscopic imperfections act as stress concentrators, decreasing the toughness further, and reducing the tensile strength. These combine to give catastrophic failures, as opposed to the ...

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Ceramic, Ceramic - Classifications of technical ceramics, Ceramic - Examples of ceramic materials, Ceramic - Properties of ceramics, Ceramic - Mechanical properties, Ceramic - Electrical properties, Ceramic - Processing of ceramic materials, Ceramic - In situ manufacturing, Ceramic - Sintering-based methods, Ceramic - Other applications of ceramics

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Terpyridine was synthesized from the oxidative coupling of pyridines at first. This method, however, has low-yield reactions and other oligomers and isomers are created, so it was necessary to separate the mixtures. In 1991, L. E. Guise et al. reported the more efficient synthesis of terpyridine from the condensation of 2-acetylpyridine and enaminone, which is prepared by the reaction of 2-acetylpyridine ...

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Terpyridine, Terpyridine - History, Terpyridine - Synthesis, Terpyridine - Properties, Terpyridine - Related compounds

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Mercury was known to the ancient Chinese and Hindus and was found in Egyptian tombs that date from 1500 BCE. In China, India and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health. The ancient Greeks used mercury in ointments and the Romans used it in cosmetics. By 500 BCE mercury was used to make amalgams with other metals. The Indian word for alchemy is Rassayana which means ‘the way of mercury.’ Alchemists often thought of mercury as the first matter from which all metals w ...

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Mercury element, Mercury element - Applications, Mercury element - History, Mercury element - Dentistry, Mercury element - Medicine, Mercury element - Mineral occurrence, Mercury element - Compounds, Mercury element - Isotopes, Mercury element - Occurrence in the environment, Mercury element - Health and Environmental Effects, Mercury element - Precautions and regulation, Mercury element - Occupational exposure, Mercury element - Mercury in fish, Mercury element - Release of mercury into the environment, Mercury element - Mercury and aluminum

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Electron spin resonance - Units and constants. A magnetic Field is described by some constants and units: Magnetic induction in tesla (T) Magnetic flux density in amperes per metre (A/m) and relationship: The CGS unit for magnetic induction is the gauss (G) which is equivalent to 10-4 T Furthermore, in describing EPR, following units are very important: Planck's constant h = 6.63 x 10See also:

Electron spin resonance, Electron spin resonance - EPR theory, Electron spin resonance - Units and constants, Electron spin resonance - Basics, Electron spin resonance - Boltzmann distribution, Electron spin resonance - EPR spectral parameters, Electron spin resonance - The g factor, Electron spin resonance - Resonance linewidth definition

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Many metal sulfides are so insoluble that they are probably not very toxic. Some metal sulfides, when exposed to a strong mineral acid - and this includes your stomach acids - , will release toxic hydrogen sulfide. Organic sulfides are of course highly flammable. When a sulfide burns, the fumes usually include toxic sulfur dioxide (SO2) gas. Meyer, B.; Ward, K.; Koshlap, K.; & Peter ...

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Sulfide, Sulfide - Examples, Sulfide - Uses, Sulfide - Natural occurrence, Sulfide - Safety

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The major use for tantalum, as tantalum metal powder, is in the production of electronic components, mainly tantalum capacitors. Tantalum electrolytic capacitors exploit the natural tendency of tantalum to form a protective oxide surface layer, using tantalum foil as one plate of the capacitor, the oxide as the dielectric, and an electrolytic solution as the other plate. Because the dielectric layer can be very thin (thinner than the similar layer in, for instance, an aluminium electrolytic capacitor), a high capacitance can be achieved in a ...

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Tantalum, Tantalum - Notable characteristics, Tantalum - Applications, Tantalum - History, Tantalum - Occurrence, Tantalum - Compounds, Tantalum - Isotopes, Tantalum - Precautions

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Mercury was known to the ancient Chinese and Hindus and was found in Egyptian tombs that date from 1500 BCE. In China, India and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health. The ancient Greeks used mercury in ointments and the Romans used it in cosmetics. By 500 BCE mercury was used to make amalgams with other metals. The Indian word for alchemy is Rassayana which means ‘the way of mercury.’ Alchemists often thought of mercury as the first matter from which all metals w ...

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Mercury element, Mercury element - Applications, Mercury element - History, Mercury element - Dentistry, Mercury element - Medicine, Mercury element - Mineral occurrence, Mercury element - Compounds, Mercury element - Isotopes, Mercury element - Occurrence in the environment, Mercury element - Health and Environmental Effects, Mercury element - Precautions and Regulation

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The industrial extraction of rhodium is complex as the metal occurs in ores mixed with other metals such as palladium, silver, platinum, and gold. It is found in platinum ores and obtained free as a white inert metal which it is very difficult to fuse. Principal sources of this element are located in South Africa, in river sands of the Ural Mountains, in North and South America and also in the copper-nickel sulfide mining area of the Sudbury, Ontario region. Although the quantity at Sudbury is very small, the large amount of nickel ore proce ...

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Rhodium, Rhodium - Notable characteristics, Rhodium - Applications, Rhodium - History, Rhodium - Occurrence, Rhodium - Isotopes, Rhodium - Precautions

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It was first created at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany on December 8, 1994. Only three atoms of it were observed (all 272Rg), by the fusion of bismuth-209 and nickel-64 in a linear accelerator. (Nickel was bombarded onto the bismuth target.) The name roentgenium was accepted as a permanent name on November 1, 2004 in honour of Wilhelm Roentgen; before this date, the element was known under the temporary IUPAC systematic element name unununium. Some res ...

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Roentgenium, Roentgenium - History, Roentgenium - Isotopes

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Most commonly, photolytic, thermal, or transition metal catalyzed decomposition of diazoalkanes is used to create carbene molecules. A variation on catalyzed decomposition of diazoalkanes is the Bamford-Stevens reaction, which gives carbenes in aprotic solvents and carbenium ions in protic solvents. Another method is induced elimination of halogen from gem-dihalides or HX from CHX3 moiety, employing organolithium reagents (or another strong base). It is not certain that in these reactions actual free carbenes are formed. In some c ...

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Carbene, Carbene - Generation of Carbenes, Carbene - Persistent carbenes

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A polyvalent hard white metal, ruthenium is a member of the platinum group, has four crystal modifications and does not tarnish at normal temperatures, but does oxidize explosively. Ruthenium dissolves in fused alkalis, is not attacked by acids but is attacked by halogens at high temperatures and by hydroxides. Small amounts of ruthenium can increase the hardness of platinum and palladium. The corrosion resistance of titanium is increased mar ...

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Ruthenium, Ruthenium - Notable characteristics, Ruthenium - Applications, Ruthenium - History, Ruthenium - Occurrence, Ruthenium - Compounds, Ruthenium - Isotopes, Ruthenium - Organometallic chemistry, Ruthenium - Precautions

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Titanium is well known for its excellent corrosion resistance (almost as resistant as platinum), being able to withstand attack by acids, moist chlorine gas, and by common salt solutions. Pure titanium is not soluble in water but is soluble in concentrated acids. A metallic element, it is also well-known for its high strength-to-weight ratio. It is a light, strong metal with low density (60% as dense as steel) that, when pure, is quite ductile (especially in an oxygen-free environment), easy to work, lustrous, and metallic-white in colour. T ...

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Titanium, Titanium - Notable characteristics, Titanium - Applications, Titanium - History, Titanium - Occurrence and production, Titanium - Compounds, Titanium - Isotopes, Titanium - Precautions

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Yttrium(III) oxide is the most important yttrium compound and is widely used to make YVO4 europium and Y2O3 europium phosphors that give the red color in color television picture tubes. Other uses; Yttrium oxide is also used to make yttrium-iron garnets which are very effective microwave filters. Yttrium iron, aluminium, and gadolinium garnets (e.g. Y3Fe5O12 and Y3Al5O12) have interesting magnetic properties. Yttrium iron ...

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Yttrium, Yttrium - Notable Characteristics, Yttrium - Applications, Yttrium - History, Yttrium - Occurrence, Yttrium - Isotopes, Yttrium - Precautions

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Ammonia is a colourless gas with a characteristic pungent smell; it is lighter than air, its density being 0.589 times that of air. It is easily liquefied and the liquid boils at -33.7 °C, and solidifies at -75 °C to a mass of white crystals. Liquid ammonia possesses strong ionizing powers (ε = 22), and solutions of salts in liquid ammonia have been much studied. Liquid ammonia has a very high standard enthalpy change of vaporization (23.35 kJ/mol, c.f. water 40.65 kJ/mol, methane 8.19 kJ/mol, phosphine 14.6 kJ/mol) and can therefore be used in laboratories in non-insulated vessels at room temperature, even thou ...

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Ammonia, Ammonia - History, Ammonia - Production, Ammonia - Properties, Ammonia - Formation of salts, Ammonia - Acidity, Ammonia - Formation of other compounds, Ammonia - Ammonia as a ligand, Ammonia - Uses, Ammonia - Liquid ammonia as a solvent, Ammonia - Solubility of salts, Ammonia - Solutions of metals, Ammonia - Redox properties of liquid ammonia, Ammonia - Detection and determination, Ammonia - Safety precautions, Ammonia - Toxicity, Ammonia - Household use, Ammonia - Laboratory use of ammonia solutions, Ammonia - Laboratory use of anhydrous ammonia gas or liquid, Ammonia - Reference, Ammonia - Bibliography

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A platinum family metal, iridium is white, resembling platinum, but with a slight yellowish cast. Due to its extreme hardness and brittle properties, iridium is difficult to machine, form, or work. Iridium is the most corrosion-resistant metal known. Iridium cannot be attacked by any acids or by aqua regia, but it can be attacked by molten salts, such as NaCl and NaCN. The measured density of this element is only slightly lower than that of osmium, which is therefore often listed as the heaviest element known. However, calculations of ...

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Iridium, Iridium - Notable characteristics, Iridium - Applications, Iridium - History, Iridium - Occurrence, Iridium - Isotopes, Iridium - Precautions

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Gold is a metallic element with a characteristic yellow color, but can also be black or ruby when finely divided, while colloidal solutions are intensely colored and often purple. These colors are the result of gold's plasmon frequency lying in the visible range, which causes red and yellow light to be reflected, and blue light to be absorbed. Only silver colloids exhibit the same interactions with light, albeit at a shorter fr ...

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Gold, Gold - Notable characteristics, Gold - Applications, Gold - History, Gold - Value, Gold - Gold and the money supply, Gold - Restrictions on gold ownership, Gold - Return of a gold standard?, Gold - Gold in investment portfolios, Gold - Occurrence, Gold - Production, Gold - Compounds/isotopes, Gold - Precautions, Gold - Symbolism

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Ceramics - Mechanical properties. Ceramic materials are usually ionic or covalently-bonded materials, and can be crystalline or amorphous. A material held together by either type of bond will tend to fracture before any plastic deformation takes place, which results in poor toughness in these materials. Additionally, because these materials tend to be porous, the pores and other microscopic imperfections act as stress concentrators, decreasing the toughness further, and reducing the tensile strength. These combine to give catastrophic failures, as opposed to the ...

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Ceramics, Ceramics - Classifications of technical ceramics, Ceramics - Examples of ceramic materials, Ceramics - Properties of ceramics, Ceramics - Mechanical properties, Ceramics - Electrical properties, Ceramics - Processing of ceramic materials, Ceramics - In situ manufacturing, Ceramics - Sintering-based methods, Ceramics - Other applications of ceramics

Read more here: » Ceramics: Encyclopedia II - Ceramics - Properties of ceramics