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Lithium Fluoride
LITHIUM FLUORIDE is an inorganic compound with the chemical formula LiF. It is a colorless solid, that transitions to white with decreasing crystal size. Although odorless, lithium fluoride has a bitter-saline taste. Its structure is analogous to that of sodium chloride , but it is much less soluble in water. It is mainly used as a component of molten salts . Formation of LiF from the elements releases one of the highest energy per mass of reactants , only second to that of BeO
BeO
. CONTENTS * 1 Manufacturing * 2 Applications * 2.1 In molten salts * 2.2 Optics
Optics
* 2.3 Radiation detectors * 2.4 Nuclear reactors * 2.5 Cathode for PLED and OLEDs * 2.6 Natural occurrence * 3 References MANUFACTURINGLiF is prepared from lithium hydroxide or lithium carbonate with hydrogen fluoride
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Chemical Nomenclature
A CHEMICAL NOMENCLATURE is a set of rules to generate systematic names for chemical compounds . The nomenclature used most frequently worldwide is the one created and developed by the International Union of Pure and Applied Chemistry (IUPAC). The IUPAC's rules for naming organic and inorganic compounds are contained in two publications, known as the _Blue Book _ and the _Red Book _, respectively. A third publication, known as the _Green Book _, describes the recommendations for the use of symbols for physical quantities (in association with the IUPAP ), while a fourth, the _Gold Book _, contains the definitions of a large number of technical terms used in chemistry. Similar compendia exist for biochemistry (the _White Book_, in association with the IUBMB ), analytical chemistry (the _Orange Book _), macromolecular chemistry (the _Purple Book_) and clinical chemistry (the _Silver Book_)
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Standard Molar Entropy
In chemistry , the STANDARD MOLAR ENTROPY is the entropy content of one mole of substance under a standard state (not STP ). The standard molar entropy is usually given the symbol S°, and as units of joules per mole kelvin (J mol−1 K−1). Unlike standard enthalpies of formation , the value of S° is absolute. That is, an element in its standard state has a definite, nonzero value of S at room temperature. The entropy of a pure crystalline structure can be 0 J mol−1 K−1 only at 0 K, according to the third law of thermodynamics . However, this presupposes that the material forms a 'perfect crystal ' without any frozen in entropy (defects, dislocations), which is never completely true because crystals always grow at a finite temperature. However this residual entropy is often quite negligible
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NFPA 704
"NFPA 704: STANDARD SYSTEM FOR THE IDENTIFICATION OF THE HAZARDS OF MATERIALS FOR EMERGENCY RESPONSE" is a standard maintained by the U.S. -based National Fire Protection Association . First "tentatively adopted as a guide" in 1960, and revised several times since then, it defines the colloquial "FIRE DIAMOND" used by emergency personnel to quickly and easily identify the risks posed by hazardous materials. This helps determine what, if any, special equipment should be used, procedures followed, or precautions taken during the initial stages of an emergency response. CONTENTS * 1 Codes * 2 See also * 3 References * 4 External links CODESThe four divisions are typically color-coded with red indicating flammability , blue indicating level of health hazard, yellow for chemical reactivity , and white containing codes for special hazards. Each of health, flammability and reactivity is rated on a scale from 0 (no hazard) to 4 (severe risk)
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Molecular Geometry
MOLECULAR GEOMETRY is the three-dimensional arrangement of the atoms that constitute a molecule . It determines several properties of a substance including its reactivity , polarity , phase of matter , color , magnetism and biological activity . The angles between bonds that an atom forms depend only weakly on the rest of molecule, i.e. they can be understood as approximately local and hence transferable properties . CONTENTS * 1 Determination * 2 The influence of thermal excitation * 3 Bonding * 4 Isomers * 5 Types of molecular structure * 5.1 VSEPR table * 6 3D representations * 7 See also * 8 References * 9 External links DETERMINATIONThe molecular geometry can be determined by various spectroscopic methods and diffraction methods. IR , microwave and Raman spectroscopy can give information about the molecule geometry from the details of the vibrational and rotational absorbance detected by these techniques
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Lattice Constant
The LATTICE CONSTANT, or LATTICE PARAMETER, refers to the physical dimension of unit cells in a crystal lattice . Lattices in three dimensions generally have three lattice constants, referred to as a, b, and c. However, in the special case of cubic crystal structures , all of the constants are equal and we only refer to a. Similarly, in hexagonal crystal structures , the a and b constants are equal, and we only refer to the a and c constants. A group of lattice constants could be referred to as LATTICE PARAMETERS. However, the full set of lattice parameters consist of the three lattice constants and the three angles between them. For example, the lattice constant for diamond is a = 3.57 Å at 300 K . The structure is equilateral although its actual shape cannot be determined from only the lattice constant. Furthermore, in real applications, typically the average lattice constant is given
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Magnetic Susceptibility
In electromagnetism , the MAGNETIC SUSCEPTIBILITY ( Latin : _susceptibilis_, "receptive"; denoted χ ) is one measure of the magnetic properties of a material. The susceptibility indicates whether a material is attracted into or repelled out of a magnetic field, which in turn has implications for practical applications. Quantitative measures of the magnetic susceptibility also provide insights into the structure of materials, providing insight into bonding and energy levels
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Refractive Index
In optics , the REFRACTIVE INDEX or INDEX OF REFRACTION _n_ of a material is a dimensionless number that describes how light propagates through that medium. It is defined as n = c v , {displaystyle n={frac {c}{v}},} where _c_ is the speed of light in vacuum and _v_ is the phase velocity of light in the medium. For example, the refractive index of water is 1.333, meaning that light travels 1.333 times faster in a vacuum than it does in water. Refraction
Refraction
of a light ray The refractive index determines how much light is bent, or refracted , when entering a material. This is the first documented use of refractive indices and is described by Snell\'s law of refraction, _n_1 sin_θ_1 = _n_2 sin_θ_2, where _θ_1 and _θ_2 are the angles of incidence and refraction, respectively, of a ray crossing the interface between two media with refractive indices _n_1 and _n_2
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Crystal Structure
In crystallography , CRYSTAL STRUCTURE is a description of the ordered arrangement of atoms , ions or molecules in a crystalline material . Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter. The smallest group of particles in the material that constitutes the repeating pattern is the UNIT CELL of the structure. The unit cell completely defines the symmetry and structure of the entire crystal lattice, which is built up by repetitive translation of the unit cell along its principal axes. The repeating patterns are said to be located at the points of the Bravais lattice . The lengths of the principal axes, or edges, of the unit cell and the angles between them are the lattice constants , also called _lattice parameters_. The symmetry properties of the crystal are described by the concept of space groups
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Ion
An ION (/ˈaɪən, -ɒn/ ) is an atom , or a molecule , in which the total number of electrons is not equal to the total number of protons , giving the atom or molecule a net positive or negative electrical charge . An atom, or molecule, with a net positive charge is a cation . An atom, or molecule, with a net negative charge is an anion . Because of their opposite electric charges, cations and anions attract each other and readily form ionic compounds , such as salts . Ions can be created by chemical means, such as the dissolution of a salt into water, or by physical means, such as passing a direct current through a conducting solution, which will dissolve the anode via ionization . Ions consisting of only a single atom are atomic or monatomic ions . If they consist of two or more atoms, then they are called either molecular ions , or polyatomic ions
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Francium Fluoride
FRANCIUM is a chemical element with symbol FR and atomic number 87. It used to be known as eka -caesium and actinium K. It is the second-least electronegative element, behind only caesium, and is the second rarest naturally occurring element (after astatine ). Francium is a highly radioactive metal that decays into astatine , radium , and radon . As an alkali metal , it has one valence electron . Bulk francium has never been viewed. Because of the general appearance of the other elements in its periodic table column, it is assumed that francium would appear as a highly reactive metal, if enough could be collected together to be viewed as a bulk solid or liquid. Obtaining such a sample is highly improbable, since the extreme heat of decay (the half-life of its longest-lived isotope is only 22 minutes) would immediately vaporize any viewable quantity of the element
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BeO
BERYLLIUM OXIDE (BEO), also known as BERYLLIA, is an inorganic compound with the formula BeO. This colourless solid is a notable electrical insulator with a higher thermal conductivity than any other non-metal except diamond , and exceeds that of most metals. As an amorphous solid , beryllium oxide is white. Its high melting point leads to its use as a refractory . It occurs in nature as the mineral bromellite . Historically and in materials science, beryllium oxide was called GLUCINA or glucinium oxide. Formation of BeO from beryllium and oxygen releases the highest energy per mass of reactants for any chemical reaction, close to 24 MJ/kg
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Electrolysis
In chemistry and manufacturing , ELECTROLYSIS is a technique that uses a direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis
Electrolysis
is commercially important as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell . The voltage that is needed for electrolysis to occur is called the decomposition potential
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Electrode
An ELECTRODE is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor , an electrolyte , a vacuum or air). The word was coined by William Whewell at the request of the scientist Michael Faraday from the Greek words _elektron_, meaning amber (from which the word electricity is derived), and _hodos_, a way. The electrophore , invented by Volta is an early version of an electrode used to study static electricity
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Energy Density
ENERGY DENSITY is the amount of energy stored in a given system or region of space per unit volume . Colloquially it may also be used for energy per unit mass , though the accurate term for this is specific energy . Often only the useful or extractable energy is measured, which is to say that inaccessible energy (such as rest mass energy) is ignored. In cosmological and other general relativistic contexts, however, the energy densities considered are those that correspond to the elements of the stress–energy tensor and therefore do include mass energy as well as energy densities associated with the pressures described in the next paragraph
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Molten Salt
MOLTEN SALT is salt which is solid at standard temperature and pressure (STP) but enters the liquid phase due to elevated temperature. A salt that is normally liquid even at STP is usually called a room temperature ionic liquid , although technically molten salts are a class of ionic liquids. CONTENTS * 1 Uses * 2 Ambient temperature molten salts * 3 See also * 4 References * 5 Bibliography USESMolten salts have a variety of uses. Molten chloride salt mixtures are commonly used as baths for various alloy heat treatments , such as annealing and martempering of steel . Cyanide
Cyanide
and chloride salt mixtures are used for surface modification of alloys such as carburizing and nitrocarburizing of steel. Cryolite
Cryolite
(a fluoride salt) is used as a solvent for aluminium oxide in the production of aluminium in the Hall-Héroult process