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Barium Bromide
Barium bromide is the chemical compound with the formula BaBr2. It is ionic in nature. Structure and properties BaBr2 crystallizes in the lead chloride (cotunnite) motif, giving white orthorhombic crystals that are deliquescent. In aqueous solution BaBr2 behaves as a simple salt. Solutions of barium bromide reacts with the sulfate salts to produce a solid precipitate of barium sulfate. :BaBr2 + → BaSO4 + 2 Br− Similar reactions occur with oxalic acid, hydrofluoric acid, and phosphoric acid, giving solid precipitates of barium oxalate, fluoride, and phosphate, respectively. Preparation Barium bromide can be prepared by treating barium sulfide or barium carbonate with hydrobromic acid: :BaS + 2 HBr → BaBr2 + H2S :BaCO3 + 2 HBr → BaBr2 + CO2 + H2O Barium bromide crystallizes from concentrated aqueous solution in its di hydrate , BaBr2·2H2O. Heating this dihydrate to 120 °C gives the anhydrous salt. Uses Barium bromide is a precursor t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space-filling Model
In chemistry, a space-filling model, also known as a ''calotte model'', is a type of three-dimensional (3D) molecular model where the atoms are represented by spheres whose radii are proportional to the radii of the atoms and whose center-to-center distances are proportional to the distances between the atomic nuclei, all in the same scale. Atoms of different chemical elements are usually represented by spheres of different colors. Space-filling calotte models are also referred to as CPK models after the chemists Robert Corey, Linus Pauling, and Walter Koltun, who over a span of time developed the modeling concept into a useful form. They are distinguished from other 3D representations, such as the ball-and-stick and skeletal models, by the use of the "full size" space-filling spheres for the atoms. The models are tactile and manually rotatable. They are useful for visualizing the effective shape and relative dimensions of a molecule, and (because of the rotatability) the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ionic Compound
In chemistry, an ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. The compound is neutral overall, but consists of positively charged ions called cations and negatively charged ions called anions. These can be simple ions such as the sodium (Na+) and chloride (Cl−) in sodium chloride, or polyatomic species such as the ammonium () and carbonate () ions in ammonium carbonate. Individual ions within an ionic compound usually have multiple nearest neighbours, so are not considered to be part of molecules, but instead part of a continuous three-dimensional network. Ionic compounds usually form crystalline structures when solid. Ionic compounds containing basic ions hydroxide (OH−) or oxide (O2−) are classified as bases. Ionic compounds without these ions are also known as salts and can be formed by acid–base reactions. Ionic compounds can also be produced from their constituent ions by evaporation of their ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ball-and-stick Model
In chemistry, the ball-and-stick model is a molecular model of a chemical substance which displays both the three-dimensional position of the atoms and the bonds between them. The atoms are typically represented by spheres, connected by rods which represent the bonds. Double and triple bonds are usually represented by two or three curved rods, respectively, or alternately by correctly positioned sticks for the sigma and pi bonds. In a good model, the angles between the rods should be the same as the angles between the bonds, and the distances between the centers of the spheres should be proportional to the distances between the corresponding atomic nuclei. The chemical element of each atom is often indicated by the sphere's color. In a ball-and-stick model, the radius of the spheres is usually much smaller than the rod lengths, in order to provide a clearer view of the atoms and bonds throughout the model. As a consequence, the model does not provide a clear insight about th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coordination Sphere
In coordination chemistry, the first coordination sphere refers to the array of molecules and ions (the ligands) directly attached to the central metal atom. The second coordination sphere consists of molecules and ions that attached in various ways to the first coordination sphere. First coordination sphere The first coordination sphere refers to the molecules that are attached directly to the metal. The interactions between the first and second coordination spheres usually involve hydrogen-bonding. For charged complexes, ion pairing is important. In hexamminecobalt(III) chloride ( o(NH3)6l3), the cobalt cation plus the 6 ammonia ligands comprise the first coordination sphere. The coordination sphere of this ion thus consists of a central MN6 core "decorated" by 18 N−H bonds that radiate outwards. Second coordination sphere Metal ions can be described as consisting of series of two concentric coordination spheres, the first and second. More distant from the second coo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambridge Crystallographic Data Centre
The Cambridge Crystallographic Data Centre (CCDC) is a non-profit organisation based in Cambridge, England. Its primary activity is the compilation and maintenance of the Cambridge Structural Database, a database of small molecule crystal structures. They also perform analysis on the database for the benefit of the scientific community, and write and distribute computer software to allow others to do the same. History In 1962, Dr. Olga Kennard OBE FRS set up a chemical crystallography group within the Department of Chemistry, University of Cambridge. In 1965 she founded the CCDC and established the associated Cambridge Structural Database. At that time, there were only about 3,000 published X-ray structures, and the work involved converting these into a machine-readable form. In 1992, the CCDC moved into its own building adjacent to the Cambridge chemistry department. This new headquarters was designed by the Danish architect Professor Erik Christian Sørensen and won ''The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambridge Structural Database
The Cambridge Structural Database (CSD) is both a repository and a validated and curated resource for the three-dimensional structural data of molecules generally containing at least carbon and hydrogen, comprising a wide range of organic compound, organic, metalorganic, metal-organic and organometallic molecules. The specific entries are complementary to the other crystallographic databases such as the Protein Data Bank (PDB), Inorganic Crystal Structure Database and International Centre for Diffraction Data. The data, typically obtained by X-ray crystallography and less frequently by electron diffraction or neutron diffraction, and submitted by crystallography, crystallographers and chemists from around the world, are freely accessible (as deposited by authors) on the Internet via the CSD's parent organization's website (CCDC, Repository). The CSD is overseen by the not-for-profit incorporated company called the Cambridge Crystallographic Data Centre, CCDC. The CSD is a widely ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystallography Open Database
The Crystallography Open Database (COD) is a database of crystal structures. Unlike similar crystallography databases, the database is entirely open-access, with registered users able to contribute published and unpublished structures of small molecules and small to medium sized unit cell crystals to the database. As of May 2016, the database has more than 360,000 entries. The database has various contributors, and contains Crystallographic Information Files as defined by the International Union of Crystallography (IUCr). There are currently five sites worldwide that mirror this database. The 3D structures of compounds can be converted to input files for 3D printers. See also * Crystallography * Crystallographic database A crystallographic database is a database specifically designed to store information about the structure of molecules and crystals. Crystals are solids having, in all three dimensions of space, a regularly repeating arrangement of atoms, ions, or ... Reference ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of Physical Chemistry
''The Journal of Physical Chemistry A'' is a scientific journal which reports research on the chemistry of molecules - including their dynamics, spectroscopy, kinetics, structure, bonding, and quantum chemistry. It is published weekly by the American Chemical Society. Before 1997 the title was simply ''Journal of Physical Chemistry''. Owing to the ever-growing amount of research in the area, in 1997 the journal was split into ''Journal of Physical Chemistry A'' (molecular theoretical and experimental physical chemistry) and '' The Journal of Physical Chemistry B'' (solid state, soft matter, liquids, etc.). Beginning in 2007, the latter underwent a further split, with ''The Journal of Physical Chemistry C'' now being dedicated to nanotechnology, molecular electronics, and related subjects. Editors-in-chief *1896–1932 Wilder Dwight Bancroft, Joseph E. Trevor *1933–1951 S. C. Lind *1952–1964 William A. Noyes *1965–1969 F. T. Wall *1970–1980 Bryce Crawford *1980–2004 Mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deliquescence
Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance's molecules, adsorbing substances can become physically changed, e.g., changing in volume, boiling point, viscosity or some other physical characteristic or property of the substance. For example, a finely dispersed hygroscopic powder, such as a salt, may become clumpy over time due to collection of moisture from the surrounding environment. ''Deliquescent'' materials are sufficiently hygroscopic that they absorb so much water that they become liquid and form an aqueous solution. Etymology and pronunciation The word ''hygroscopy'' () uses combining forms of '' hygro-'' and '' -scopy''. Unlike any other ''-scopy'' word, it no longer refers to a viewing or imaging mode. It did begin that way, with the word ''hygroscope'' referring in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
