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Gallium Halides
There are three sets of gallium halides, the trihalides where gallium has oxidation state +3, the intermediate halides containing gallium in oxidation states +1, +2 and +3 and some unstable monohalides, where gallium has oxidation state +1. Trihalides All four trihalides are known. They all contain gallium in the +3 oxidation state. Their proper names are gallium(III) fluoride, gallium(III) chloride, gallium(III) bromide and gallium(III) iodide. ;Gallium(III) fluoride, GaF3 :GaF3 is a white solid which sublimes before it melts, with an estimated melting point above 1000 °C. It contains 6 co-ordinate gallium atoms with a three-dimensional network of GaF6 octahedra sharing common corners. ;Gallium trichloride, GaCl3, Gallium tribromide, GaBr3 and gallium triiodide, GaI3 :These all have lower melting points than GaF3, (Gallium trichloride, GaCl3 mp 78 °C, GaBr3 mp 122 °C, GaI3 mp 212 °C) reflecting the fact that their structures all contain dimers with 4 coordin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gallium
Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, elemental gallium is a soft, silvery metal at standard temperature and pressure. In its liquid state, it becomes silvery white. If enough force is applied, solid gallium may fracture conchoidal fracture, conchoidally. Since its discovery in 1875, gallium has widely been used to make alloys with low melting points. It is also used in semiconductors, as a dopant in semiconductor substrates. The melting point of gallium, , is used as a temperature reference point. Gallium alloys are used in thermometers as a non-toxic and environmentally friendly alternative to Mercury (element), mercury, and can withstand higher temperatures than mercury. A melting point of , well below the freezing point of water, is claimed for the alloy galinstan (62–95% gallium, 5–22% indium, and 0–16% tin by weight), but that may be t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unit Cell
In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector In mathematics, a unit vector in a normed vector space is a Vector (mathematics and physics), vector (often a vector (geometry), spatial vector) of Norm (mathematics), length 1. A unit vector is often denoted by a lowercase letter with a circumfle ..., for example) does not necessarily have unit size, or even a particular size at all. Rather, the primitive cell is the closest analogy to a unit vector, since it has a determined size for a given lattice and is the basic building block from which larger cells are constructed. The concept is used particularly in describing crystal structure in two and three dimensions, though it makes sense in all dimensions. A lattice can be characterized by the geometry of its unit cell, which is a section of the tiling (a parallelogra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gallium Compounds
Gallium compounds are compounds containing the element gallium. These compounds are found primarily in the +3 oxidation state. The +1 oxidation state is also found in some compounds, although it is less common than it is for gallium's heavier congeners indium and thallium. For example, the very stable GaCl2 contains both gallium(I) and gallium(III) and can be formulated as GaIGaIIICl4; in contrast, the monochloride is unstable above 0 °C, disproportionating into elemental gallium and gallium(III) chloride. Compounds containing Ga–Ga bonds are true gallium(II) compounds, such as GaS (which can be formulated as Ga24+(S2−)2) and the dioxan complex Ga2Cl4(C4H8O2)2.Greenwood and Earnshaw, p. 240 There are also compounds of gallium with negative oxidation states, ranging from −5 to −1, most of these compounds being magnesium gallides (MgxGay). Aqueous chemistry Strong acids dissolve gallium, forming gallium(III) salts such as (gallium nitrate). Aqueous solutions o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indium Halides
There are three sets of Indium halides, the trihalides, the monohalides, and several intermediate halides. In the monohalides the oxidation state of indium is +1 and their proper names are indium(I) fluoride, indium(I) chloride, indium(I) bromide and indium(I) iodide. The intermediate halides contain indium with oxidation states, +1, +2 and +3. Indium trihalides In all of the trihalides the oxidation state of indium is +3, and their proper names are indium(III) fluoride, indium(III) chloride, indium(III) bromide, and indium(III) iodide. The trihalides are Lewis acidic. Indium trichloride is a starting point in the production of trimethylindium which is used in the semiconductor industry. Indium(III) fluoride InF3 is a white solid, m.p. 1170 °C. Its structure contains 6 coordinate indium. Indium(III) chloride InCl3 is a white solid, m.p. 586 °C. It is obtained by oxidation of indium with chlorine. It is isostructural with AlCl3. Indium(III) bromide InBr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gallium Monoiodide
Gallium monoiodide is an inorganic gallium compound with the formula GaI or Ga4I4. It is a pale green solid and mixed valent gallium compound, which can contain gallium in the 0, +1, +2, and +3 oxidation states. It is used as a pathway for many gallium-based products. Unlike the gallium(I) halides first crystallographically characterized, gallium monoiodide has a more facile synthesis allowing a synthetic route to many low-valent gallium compounds. Synthesis In 1990, Malcolm Green synthesized gallium monoiodide by the ultrasonication of liquid gallium metal with iodine in toluene yielding a pale green powder referred to as gallium monoiodide. The chemical composition of gallium monoiodide was not determined until the early to mid-2010s despite its simple synthesis. In 2012, the pale green gallium monoiodide was determined to be a combination of gallium metal and gallium(I,III) iodide, having the chemical composition a0sub>2 a+GaI4−]. However, in 2014, it was found that the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gallium(III) Nitride
Gallium nitride () is a binary III/ V direct bandgap semiconductor commonly used in blue light-emitting diodes since the 1990s. The compound is a very hard material that has a Wurtzite crystal structure. Its wide band gap of 3.4 eV affords it special properties for applications in optoelectronics, high-power and high-frequency devices. For example, GaN is the substrate that makes violet (405 nm) laser diodes possible, without requiring nonlinear optical frequency doubling. Its sensitivity to ionizing radiation is low (like other group III nitrides), making it a suitable material for solar cell arrays for satellites. Military and space applications could also benefit as devices have shown stability in high-radiation environments. Because GaN transistors can operate at much higher temperatures and work at much higher voltages than gallium arsenide (GaAs) transistors, they make ideal power amplifiers at microwave frequencies. In addition, GaN offers promising char ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydride Vapour Phase Epitaxy
Hydride vapour-phase epitaxy (HVPE) is an epitaxial growth technique often employed to produce semiconductors such as GaN, GaAs, InP and their related compounds, in which hydrogen chloride is reacted at elevated temperature with the group-III metals to produce gaseous metal chlorides, which then react with ammonia to produce the group-III nitrides. Carrier gasses commonly used include ammonia, hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ... and various chlorides. HVPE technology can significantly reduce the cost of production compared to the most common method of vapor deposition of organometallic compounds ( MOCVD). Cost reduction is achieved by significantly reducing the consumption of NH3, cheaper source materials than in MOCVD, reducing the capital equipment costs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hapticity
In coordination chemistry, hapticity is the coordination complex, coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms. The hapticity of a ligand is described with the Greek letter eta (letter), η ('eta'). For example, η2 describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated (otherwise the denticity, κ-notation is used). In addition, if the ligand coordinates through multiple atoms that are contiguous then this is considered denticity (not hapticity), and the κ-notation is used once again. When naming complexes care should be taken not to confuse η with mu (letter), μ ('mu'), which relates to bridging ligands. History The need for additional nomenclature for organometallic compounds became apparent in the mid-1950s when Dunitz, Leslie Orgel, Orgel, and Rich described the structure of the "sandwich compound, sandwich complex" ferrocene by X-ray ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disproportionation
In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation state. The reverse of disproportionation, such as when a compound in an intermediate oxidation state is formed from precursors of lower and higher oxidation states, is called ''comproportionation'', also known as ''symproportionation''. More generally, the term can be applied to any desymmetrizing reaction where two molecules of one type react to give one each of two different types: : This expanded definition is not limited to redox reactions, but also includes some molecular autoionization reactions, such as the self-ionization of water. In contrast, some authors use the term ''redistribution'' to refer to reactions of this type (in either direction) when only ligand exchange but no redox is involved and distinguish such processes from disproportionation and comproportionati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal Structure
In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter. The smallest group of particles in a material that constitutes this repeating pattern is the unit cell of the structure. The unit cell completely reflects the symmetry and structure of the entire crystal, which is built up by repetitive translation of the unit cell along its principal axes. The translation vectors define the nodes of the Bravais lattice. The lengths of principal axes/edges, of the unit cell and angles between them are lattice constants, also called ''lattice parameters'' or ''cell parameters''. The symmetry properties of a crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxidation State
In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. Conceptually, the oxidation state may be positive, negative or zero. Beside nearly-pure ionic bonding, many covalent bonds exhibit a strong ionicity, making oxidation state a useful predictor of charge. The oxidation state of an atom does not represent the "real" charge on that atom, or any other actual atomic property. This is particularly true of high oxidation states, where the ionization energy required to produce a multiply positive ion is far greater than the energies available in chemical reactions. Additionally, the oxidation states of atoms in a given compound may vary depending on Electronegativities of the elements (data page), the choice of electronegativity scale used in their calculation. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
