A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs. These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a chemical name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulae can fully specify the structure of only the simplest of molecules and chemical substances, and are generally more limited in power than are chemical names and structural formulae.
In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece.
In organic chemistry, functional groups are specific substituents or moieties within molecules that may be responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction(s) regardless of the size of the molecule it is a part of. This allows for systematic prediction of chemical reactions and behavior of chemical compounds and design of chemical syntheses. Furthermore, the reactivity of a functional group can be modified by other functional groups nearby. In organic synthesis, functional group interconversion is one of the basic types of transformations.
In chemistry, a pentose is a monosaccharide with five carbon atoms. The chemical formula of all pentoses is C
5H
10O
5, and their molecular weight is 150.13 g/mol.
In chemistry, the molar mass of a chemical compound is defined as the mass of a sample of that compound divided by the amount of substance in that sample, measured in moles. The molar mass is a bulk, not molecular, property of a substance. The molar mass is an average of many instances of the compound, which often vary in mass due to the presence of isotopes. Most commonly, the molar mass is computed from the standard atomic weights and is thus a terrestrial average and a function of the relative abundance of the isotopes of the constituent atoms on earth. The molar mass is appropriate for converting between the mass of a substance and the amount of a substance for bulk quantities.
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a chemical formula. The informal use of the term formula in science refers to the general construct of a relationship between given quantities.
The octet rule is a chemical rule of thumb that reflects the observation that main group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. The rule is especially applicable to carbon, nitrogen, oxygen, and the halogens, but also to metals such as sodium or magnesium.
Tetrazine is a compound that consists of a six-membered aromatic ring containing four nitrogen atoms with the molecular formula C2H2N4. The name tetrazine is used in the nomenclature of derivatives of this compound. Three core-ring isomers exist: 1,2,3,4-tetrazines, 1,2,3,5-tetrazines, and 1,2,4,5-tetrazines, also known as v-tetrazines, as-tetrazines and s-tetrazines respectively.
In crystallography, the cubiccrystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.
Silene, or silalkenes, are unsaturated hydrosilicons, which means that they consist only of hydrogen and silicon atoms and all bond, with the exception of one double bond, are either single or double bonds. By definition cycles are excluded, so that the silenes comprise homologous series of inorganic compounds with the general formula Si
nH
2n - 2k + 2, k > 0, where k is defined as the number of double bonds. There are no commercial sources.
In chemistry, orbital hybridisation is the concept of mixing atomic orbitals into new hybrid orbitals suitable for the pairing of electrons to form chemical bonds in valence bond theory. Hybrid orbitals are very useful in the explanation of molecular geometry and atomic bonding properties and are symmetrically disposed in space. Although sometimes taught together with the valence shell electron-pair repulsion (VSEPR) theory, valence bond and hybridisation are in fact not related to the VSEPR model.
In chemistry, the valence or valency of an element is a measure of its combining power with other atoms when it forms chemical compounds or molecules.
Cyanate is an anion with the structural formula [O=C=N]−, usually written [OCN]− or [NCO]−; or any salt containing it, such as ammonium cyanate. It is the same as the isocyanate anion and an isomer of the much less stable fulminate anion [C−≡N+O]−. It can take up a proton H+
to form isocyanic acid, H−N=C=O.
A phosphoric acid, in the general sense, is a phosphorus oxoacid in which each phosphorus atom is in the oxidation state +5, and is bonded to four oxygen atoms, one of them through a double bond, arranged as the corners of a tetrahedron. Two or more of these PO
4 tetrahedra may be connected by shared single-bonded oxygens, forming linear or branched chains, cycles, or more complex structures. The single-bonded oxygen atoms that are not shared are completed with acidic hydrogen atoms. The general formula of a phosphoric acid is Hn+2−2xPnO3n+1−x, where n is the number of phosphorus atoms and x is the number of fundamental cycles in the molecule's structure, between 0 and (n+2)/2.
In chemistry the polyhedral skeletal electron pair theory (PSEPT) provides electron counting rules useful for predicting the structures of clusters such as borane and carborane clusters. The electron counting rules were originally formulated by Kenneth Wade and were further developed by Michael Mingos and others; they are sometimes known as Wade's rules or the Wade–Mingos rules. The rules are based on a molecular orbital treatment of the bonding. These rules have been extended and unified in the form of the Jemmis mno rules.
Spiro compounds have at least two molecular rings with only one common atom. The simplest spiro compounds are bicyclic, or have a bicyclic portion as part of the larger ring system, in either case with the two rings connected through the defining single common atom. The one common atom connecting the participating rings distinguishes spiro compounds from other bicyclics: from isolated ring compounds like biphenyl that have no connecting atoms, from fused ring compounds like decalin having two rings linked by two adjacent atoms, and from bridged ring compounds like norbornane with two rings linked by two non-adjacent atoms.
In a tetrahedral molecular geometry, a central atom is located at the center with four substituents that are located at the corners of a tetrahedron. The bond angles are cos−1(−1⁄3) = 109.4712206...° ≈ 109.5° when all four substituents are the same, as in methane as well as its heavier analogues. Methane and other perfectly symmetrical tetrahedral molecules belong to point group Td, but most tetrahedral molecules have lower symmetry. Tetrahedral molecules can be chiral.
Gallium(II) telluride, GaTe, is a chemical compound of gallium and tellurium. There is research interest in the structure and electronic properties of GaTe because of the possibility that it, or related compounds, may have applications in the electronics industry. Gallium telluride can be made by reacting the elements or by metal organic vapour deposition (MOCVD). . GaTe produced from the elements has a monoclinic crystal structure. Each gallium atom is tetrahedrally coordinated by 3 tellurium and one gallium atom. The gallium-gallium bond length in the Ga2 unit is 2.43 Angstrom. The structure consists of layers and can be formulated as Ga24+ 2Te2−. The bonding within the layers is ionic-covalent and between the layers is predominantly van der Waals. GaTe is classified as a layered semiconductor (like GaSe and InSe which have similar structures). It is a direct band gap semiconductor with an energy of 1.65eV at room temperature. A hexagonal form can be produced by low pressure metal organic vapour deposition (MOCVD) from alkyl gallium telluride cubane-type clusters e.g. from (t-butylGa( μ3-Te))4. The core consists of a cube of eight atoms, four gallium, and four tellurium atoms. Each gallium has an attached t-butyl group and three adjacent tellurium atoms and each tellurium has three adjacent gallium atoms. The hexagonal form, which is closely related to the monoclinic form, containing Ga24+ units, converts to the monoclinic form when annealed at 500 °C.
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulas — that is, same number of atoms of each element — but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
Metals, and specifically rare-earth elements, form numerous chemical complexes with boron. Their crystal structure and chemical bonding depend strongly on the metal element M and on its atomic ratio to boron. When B/M ratio exceeds 12, boron atoms form B12 icosahedra which are linked into a three-dimensional boron framework, and the metal atoms reside in the voids of this framework. Those icosahedra are basic structural units of most allotropes of boron and boron-rich rare-earth borides. In such borides, metal atoms donate electrons to the boron polyhedra, and thus these compounds are regarded as electron-deficient solids.
