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Magnetochemistry
Magnetochemistry is concerned with the magnetic properties of chemical compounds and Chemical element, elements. Magnetic properties arise from the spin and orbital angular momentum of the electrons contained in a compound. Compounds are diamagnetic when they contain electron pair, no unpaired electrons. Molecular compounds that contain one or more unpaired electrons are paramagnetic. The magnitude of the paramagnetism is expressed as an effective magnetic moment, μeff. For first-row transition metals the magnitude of μeff is, to a first approximation, a simple function of the number of unpaired electrons, the spin-only formula. In general, spin–orbit coupling causes μeff to deviate from the spin-only formula. For the heavier transition metals, lanthanides and actinides, spin–orbit coupling cannot be ignored. Exchange interaction can occur in clusters and infinite lattices, resulting in ferromagnetism, antiferromagnetism or ferrimagnetism depending on the relative orientations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transition Metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. The lanthanide and actinide elements (the f-block) are called inner transition metals and are sometimes considered to be transition metals as well. They are lustrous metals with good electrical and thermal conductivity. Most (with the exception of group 11 and group 12) are hard and strong, and have high melting and boiling temperatures. They form compounds in any of two or more different oxidation states and bind to a variety of ligands to form coordination complexes that are often coloured. They form many useful alloys and are often employed as catalysts in elemental form or in compounds such as coordination complexes and oxides. Most are strongly paramagnetic because of their unpaired d electrons, as are many of their compounds. All of the elements that are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paramagnetic
Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, diamagnetic materials are repelled by magnetic fields and form induced magnetic fields in the direction opposite to that of the applied magnetic field. Paramagnetic materials include most chemical elements and some compounds; they have a relative magnetic permeability slightly greater than 1 (i.e., a small positive magnetic susceptibility) and hence are attracted to magnetic fields. The magnetic moment induced by the applied field is linear in the field strength and rather weak. It typically requires a sensitive analytical balance to detect the effect and modern measurements on paramagnetic materials are often conducted with a SQUID magnetometer. Paramagnetism is due to the presence of unpaired electrons in the material, so most atom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diamagnetic
Diamagnetism is the property of materials that are repelled by a magnetic field; an applied magnetic field creates an induced magnetic field in them in the opposite direction, causing a repulsive force. In contrast, paramagnetic and ferromagnetic materials are attracted by a magnetic field. Diamagnetism is a quantum mechanical effect that occurs in all materials; when it is the only contribution to the magnetism, the material is called diamagnetic. In paramagnetic and ferromagnetic substances, the weak diamagnetic force is overcome by the attractive force of magnetic dipoles in the material. The magnetic permeability of diamagnetic materials is less than the permeability of vacuum, ''μ''0. In most materials, diamagnetism is a weak effect which can be detected only by sensitive laboratory instruments, but a superconductor acts as a strong diamagnet because it entirely expels any magnetic field from its interior (the Meissner effect). Diamagnetism was first discovered whe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Faraday Balance
A Faraday balance is a device used to measure magnetic susceptibility, a property of matter is related to the force experienced by a substance in a magnetic field. Various practical devices are available for the measurement of susceptibility, with differences in the shape of the field and the way the force is measured. In the Faraday balance, the magnetic field is homogeneous. The pole pieces of the magnet are shaped so that there is a region in which the product of the field strength and the field gradient in the ''z'' direction is constant; the sample to be measured is placed in this region. The force in this case is independent of the packing of the sample and depends only on the total mass of the material present. The method is sensitive and highly reproducible, and can be applied to single crystals. The force is measured as a weight change using a torsion balance. An alternative method for measuring magnetic susceptibility is the Gouy balance. In this technique there is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gouy Balance
The Gouy balance, invented by the French physicist Louis Georges Gouy, is a device for measuring the magnetic susceptibility of a sample. The Gouy balance operates on magnetic torque, by placing the sample on a horizontal arm or beam suspended by a thin fiber, and placing either a permanent magnet or electromagnet on the other end of the arm, there is a magnetic field applied to the system, causing the coil to experience a torque causing the arm to twist or rotate. The angle of rotation can then be calculated. Background Amongst a wide range of interest in optics, Brownian motion, and experimental physics, Gouy also had a strong intrigue for the phenomena of magnetism. Gouy derived a mathematical expression showing that force is proportional to volume susceptibility for the interaction of material in a uniform magnetic field in 1889. From this derivation, Gouy proposed that balance measurements taken for tubes of material suspended in a magnetic field could evaluate his expressi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element is therefore not a compound. A compound can be transformed into a different substance by a chemical reaction, which may involve interactions with other substances. In this process, bonds between atoms may be broken or new bonds formed or both. There are four major types of compounds, distinguished by how the constituent atoms are bonded together. Molecular compounds are held together by covalent bonds; ionic compounds are held together by ionic bonds; intermetallic compounds are held together by metallic bonds; coordination complexes are held together by coordinate covalent bonds. Non-stoichiometric compounds form a disputed marginal case. A chemical formula specifies the number of atoms of each element in a compound molecule, usin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Analytical Balance
An analytical balance (or chemical ''balance'') is a class of balance designed to measure small mass in the sub-milligram range. The measuring pan of an analytical balance (0.1 mg resolution or better) is inside a transparent enclosure with doors so that dust does not collect and so any air currents in the room do not affect the balance's operation. This enclosure is often called a draft shield. The use of a mechanically vented balance safety enclosure, which has uniquely designed acrylic airfoils, allows a smooth turbulence-free airflow that prevents balance fluctuation and the measure of mass down to 1 μg without fluctuations or loss of product. Also, the sample must be at room temperature to prevent natural convection from forming air currents inside the enclosure from causing an error in reading. Single pan mechanical substitution balance is a method of maintaining consistent response throughout the useful capacity of the balance. This is achieved by maintaining a constan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Density
Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be used: \rho = \frac, where ''ρ'' is the density, ''m'' is the mass, and ''V'' is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume, although this is scientifically inaccurate this quantity is more specifically called specific weight. For a pure substance, the density is equal to its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity and packaging. Osmium is the densest known element at standard conditions for temperature and pressure. To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity "relative den ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molar Mass
In chemistry, the molar mass () (sometimes called molecular weight or formula weight, but see related quantities for usage) of a chemical substance ( element or compound) is defined as the ratio between the mass () and the amount of substance (, measured in moles) of any sample of the substance: . The molar mass is a bulk, not molecular, property of a substance. The molar mass is a ''weighted'' ''average'' of many instances of the element or 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 molecular mass (for molecular compounds) and formula mass (for non-molecular compounds, such as ionic salts) are commonly used as synonyms of molar mass, as the numerical values are identical (for all practical purposes), differing only in units ( dalton vs. g/mol o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gouy Bal
__NOTOC__ Gouy may refer to: Places Belgium *Gouy-lez-Piéton Communes in France * Gouy, Aisne, in the department of Aisne * Gouy, Seine-Maritime, in the department of Seine-Maritime * Gouy-en-Artois, in the department of Pas-de-Calais * Gouy-en-Ternois, in the department of Pas-de-Calais * Gouy-les-Groseillers, in the department of Oise * Gouy-Saint-André, in the department of Pas-de-Calais * Gouy-Servins, in the department of Pas-de-Calais * Gouy-sous-Bellonne, in the department of Pas-de-Calais Other uses *Louis Georges Gouy, a French physicist **Gouy balance {{disambig, geo, surname ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evans Balance
Evans or Evan's may refer to: People * Evans (surname) * List of people with surname Evans * Evans Welch, Trinidad and Tobago politician Places United States * Evans Island, an island of Alaska * Evans, Colorado * Evans, Georgia * Evans County, Georgia * Evans, New York *Evans Mills, New York * Evans City, Pennsylvania * Evans, West Virginia Elsewhere * Évans, in France * Cape Evans, in Antarctica Creeks * Evans Creek (Peters Creek), a tributary of Peters Creek in California * Evans Creek (Tuscarawas River), a stream in Ohio * Evans Creek (Devils River), a stream in Texas Businesses and organizations * Robert B. Evans, founder of Evans Industries * Evans (retailer), of the United Kingdom * Evans Cycles, a United Kingdom bicycle retailer *Bob Evans Restaurants, a chain operated by Bob Evans Farms, Inc. of the United States * H. C. Evans, a defunct manufacturer of casino, amusement park and fairground equipment in the United States * D'Addario (manufacturer), a drumhead manu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calibrated
In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known accuracy, a device generating the quantity to be measured such as a voltage, a sound tone, or a physical artifact, such as a meter ruler. The outcome of the comparison can result in one of the following: * no significant error being noted on the device under test * a significant error being noted but no adjustment made * an adjustment made to correct the error to an acceptable level Strictly speaking, the term "calibration" means just the act of comparison and does not include any subsequent adjustment. The calibration standard is normally traceable to a national or international standard held by a metrology body. BIPM Definition The formal definition of calibration by the International Bureau of Weights and Measures (BIPM) is the foll ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
