|
Rubidium Superoxide
Rubidium superoxide or Rubidium hyperoxide is a compound with the formula . In terms of oxidation states, the negatively charged superoxide and positively charged rubidium give it a structural formula of (Rb+)(O2−). Chemistry It can be created by slowly exposing elemental rubidium to oxygen gas: :Rb(s) + O2(g) → RbO2(s) Like other alkali metal hyperoxides, crystals can also be grown in liquid ammonia. Between 280 and 360 °C, Rubidium superoxide will decompose, leaving not rubidium sesquioxide (Rb2O3), but rather rubidium peroxide (Rb2O2). :RbO2 (s) → 1/2 R2O2(s) + 1/2 O2(g) An even more oxygen rich compound, that of rubidium ozonide (RbO3) can be created using RbO2. Properties Roughly speaking, RbO2 has a crystal structure similar to tetragonal calcium carbide, but is rather distorted due to the Jahn–Teller effect, which makes the crystal structure less symmetrical. RbO2 is stable in dry air, but is extremely hygroscopic. The compound has been studied as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithium Superoxide
Lithium superoxide is an unstable inorganic salt with formula Li O2. A radical compound, it can be produced at low temperature in matrix isolation experiments, or in certain nonpolar, non-protic solvents. Lithium superoxide is also a transient species during the reduction of oxygen in a lithium–air galvanic cell, and serves as a main constraint on possible solvents for such a battery. For this reason, it has been investigated thoroughly using a variety of methods, both theoretical and spectroscopic. Structure The LiO2 molecule is a misnomer: the bonds between lithium and oxygen are highly ionic, with almost complete electron-transfer. The force constant between the two oxygen atoms matches the constants measured for the superoxide anion (O2−) in other contexts. The bond length for the O-O bond was determined to be 1.34 Å. Using a simple crystal structure optimization, the Li-O bond was calculated to be approximately 2.10 Å. There have been quite a few studies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous waste, particularly among aquatic organisms, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to 45% of the world's food and fertilizers. Around 70% of ammonia is used to make fertilisers in various forms and composition, such as urea and Diammonium phosphate. Ammonia in pure form is also applied directly into the soil. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceutical products and is used in many commercial cleaning products. It is mainly collected by downward displacement of both air and water. Although common in nature—both terrestrially and in the outer planets of the Solar System—and in wide use, ammonia is both caust ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neel Temperature
In physics and materials science, the Curie temperature (''T''C), or Curie point, is the temperature above which certain materials lose their permanent magnetic properties, which can (in most cases) be replaced by induced magnetism. The Curie temperature is named after Pierre Curie, who showed that magnetism was lost at a critical temperature. The force of magnetism is determined by the magnetic moment, a dipole moment within an atom which originates from the angular momentum and spin of electrons. Materials have different structures of intrinsic magnetic moments that depend on temperature; the Curie temperature is the critical point at which a material's intrinsic magnetic moments change direction. Permanent magnetism is caused by the alignment of magnetic moments and induced magnetism is created when disordered magnetic moments are forced to align in an applied magnetic field. For example, the ordered magnetic moments (ferromagnetic, Figure 1) change and become disordere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antiferromagnetic
In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions. This is, like ferromagnetism and ferrimagnetism, a manifestation of ordered magnetism. The phenomenon of antiferromagnetism was first introduced by Lev Landau in 1933. Generally, antiferromagnetic order may exist at sufficiently low temperatures, but vanishes at and above the Néel temperature – named after Louis Néel, who had first identified this type of magnetic ordering. Above the Néel temperature, the material is typically paramagnetic. Measurement When no external field is applied, the antiferromagnetic structure corresponds to a vanishing total magnetization. In an external magnetic field, a kind of ferrimagnetic behavior may be displayed in the antiferromagnetic phase, with the absolute value of one of the sublattice magneti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mott Insulator
Mott insulators are a class of materials that are expected to conduct electricity according to conventional band theories, but turn out to be insulators (particularly at low temperatures). These insulators fail to be correctly described by band theories of solids due to their strong electron–electron interactions, which are not considered in conventional band theory. A Mott transition is a transition from a metal to an insulator, driven by the strong interactions between electrons. One of the simplest models that can capture Mott transition is the Hubbard model. The band gap in a Mott insulator exists between bands of like character, such as 3d electron bands, whereas the band gap in charge-transfer insulators exists between anion and cation states, such as between O 2p and Ni 3d bands in NiO. History Although the band theory of solids had been very successful in describing various electrical properties of materials, in 1937 Jan Hendrik de Boer and Evert Johannes Willem Ve ... [...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 atoms wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Shell
In chemistry and atomic physics, an electron shell may be thought of as an orbit followed by electrons around an atom's nucleus. The closest shell to the nucleus is called the "1 shell" (also called the "K shell"), followed by the "2 shell" (or "L shell"), then the "3 shell" (or "M shell"), and so on farther and farther from the nucleus. The shells correspond to the principal quantum numbers (''n'' = 1, 2, 3, 4 ...) or are labeled alphabetically with the letters used in X-ray notation (K, L, M, ...). A useful guide when understanding electron shells in atoms is to note that each row on the conventional periodic table of elements represents an electron shell. Each shell can contain only a fixed number of electrons: the first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the ''n''th shell can in principle hold up to 2( ''n''2) electrons. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hygroscopy
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] |
Jahn–Teller Effect
The Jahn–Teller effect (JT effect or JTE) is an important mechanism of spontaneous symmetry breaking in molecular and solid-state systems which has far-reaching consequences in different fields, and is responsible for a variety of phenomena in spectroscopy, stereochemistry, crystal chemistry, molecular and solid-state physics, and materials science. The effect is named for Hermann Arthur Jahn and Edward Teller, who first reported studies about it in 1937.Bunker, Philip R.; Jensen, Per (1998) ''Molecular Symmetry and Spectroscopy'' (2nd ed.). NRC Research Press, Ottaw/ref> Simplified overview The Jahn–Teller effect, sometimes also referred to as Jahn–Teller distortion, describes the geometrical distortion of molecules and ions that result from certain electron configurations. The Jahn–Teller theorem essentially states that any non-linear molecule with a spatially degenerate energy level, degenerate electronic ground state will undergo a geometrical distortion that removes th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcium Carbide
Calcium carbide, also known as calcium acetylide, is a chemical compound with the chemical formula of Ca C2. Its main use industrially is in the production of acetylene and calcium cyanamide. The pure material is colorless, while pieces of technical-grade calcium carbide are grey or brown and consist of about 80–85% of CaC2 (the rest is CaO (calcium oxide), Ca3P2 (calcium phosphide), CaS (calcium sulfide), Ca3N2 (calcium nitride), SiC (silicon carbide), etc.). In the presence of trace moisture, technical-grade calcium carbide emits an unpleasant odor reminiscent of garlic. Applications of calcium carbide include manufacture of acetylene gas, generation of acetylene in carbide lamps, manufacture of chemicals for fertilizer, and steelmaking. Production Calcium carbide is produced industrially in an electric arc furnace from a mixture of lime and coke at approximately . This is an endothermic reaction requiring per mole and high temperatures to drive off the carbon monoxide. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rubidium Ozonide
Rubidium ozonide is an oxygen rich compound of rubidium. It is an ozonide, meaning it contains the ozonide anion (O3−). It can be created by reacting rubidium superoxide (RbO2) with ozone (O3) in a liquid ammonia solution. :RbO2 + O3 -> RbO3 + O2 The chemical forms in two crystal structures, the low temperature α-RbO3 (P21), and β-RbO3 (P21/c) Detailed structural analysis finds the ozonide anions are significantly off-center from the surrounding rubidium atoms. Since ozonide anion is magnetic, electron paramagnetic resonance Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a method for studying materials that have unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but the spin ... measurements of rubidium ozonide have determined the g-values of the ozonide anion. References Rubidium compounds Ozonides {{inorganic-compound-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rubidium Peroxide
Rubidium peroxide is rubidium's peroxide with the chemical formula Rb2O2. Production Rubidium peroxide can be produced by rapidly oxidizing rubidium in liquid ammonia at −50°C. Georg Brauer (Hrsg.), unter Mitarbeit von Marianne Baudler u. a.: ''Handbuch der Präparativen Anorganischen Chemie.'' 3., umgearbeitete Auflage. Band II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3, S. 955. ::\mathrm It can also produced by pyrolysis of rubidium superoxide in vacuum. ::\mathrm Properties Rubidium peroxide is a colourless to light yellow solid with the orthorhombic crystal structure In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a .... References {{Rubidium compounds Rubidium compounds Peroxides ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
-3D-balls.png "Click for more on -> Ammonia")
-3D-balls.png "Click for more on -> Jahn–Teller Effect")