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Actinium Oxide
Actinium(III) oxide is a chemical compound containing the rare radioactive element actinium. It has the molecular formula Ac2O3. It is similar to its corresponding lanthanum compound, lanthanum(III) oxide, and contains actinium in the oxidation state +3.Actinium (in Russian) Actinium oxide is not to be confused with Ac2O ( acetic anhydride
Acetic anhydride, or ethanoic anhydride, is the chemical compound with the chemical formula ...
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Pearson Symbol
The Pearson symbol, or Pearson notation, is used in crystallography as a means of describing a crystal structure. It was originated by William Burton Pearson and is used extensively in Pearson's handbook of crystallographic data for intermetallic phases. The symbol is made up of two letters followed by a number. For example: * Diamond structure, cF8 * Rutile structure, tP6 Construction The two letters in the Pearson symbol specify the Bravais lattice, and more specifically, the lower-case letter specifies the Crystal system, crystal family, while the upper-case letter the Lattice (group), lattice type. The number at the end of the Pearson symbol gives the number of the atoms in the conventional unit cell (atoms which satisfy 1 > x,y,z \geq 0 for the atom's position (x,y,z) in the unit cell). [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lanthanum(III) Oxide
Lanthanum(III) oxide, also known as lanthana, chemical formula , is an inorganic compound containing the rare earth element lanthanum and oxygen. It is used in some ferroelectric materials, as a component of optical materials, and is a feedstock for certain catalysts, among other uses. Properties Lanthanum oxide is a white solid that is insoluble in water, but dissolves in acidic solutions. absorbs moisture from air, converting to lanthanum hydroxide. Lanthanum oxide has p-type semiconducting properties and a band gap of approximately 5.8 eV. Its average room temperature resistivity is 10 kΩ·cm, which decreases with an increase in temperature. has the lowest lattice energy of the rare earth oxides, with very high dielectric constant ε = 27. Structure At low temperatures, has an A- hexagonal crystal structure. The metal atoms are surrounded by a 7 coordinate group of atoms, the oxygen ions are in an octahedral shape around the metal atom and there is one oxygen ion above ... [...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] |
Actinium
Actinium is a chemical element; it has chemical symbol, symbol Ac and atomic number 89. It was discovered by Friedrich Oskar Giesel in 1902, who gave it the name ''emanium''; the element got its name by being wrongly identified with a substance André-Louis Debierne found in 1899 and called actinium. The actinide series, a set of 15 elements between actinium and lawrencium in the periodic table, are named for actinium. Together with polonium, radium, and radon, actinium was one of the first Primordial element, non-primordial radioactive elements to be discovered. A soft, silvery-white radioactive metal, actinium reacts rapidly with oxygen and moisture in air forming a white coating of actinium oxide that prevents further oxidation. As with most lanthanides and many actinides, actinium assumes oxidation state +3 in nearly all its chemical compounds. Actinium is found only in traces in uranium and thorium ores as the isotope 227Ac, which decays with a half-life of 21.772 years, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Formula
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 since it does not contain any 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 chemical names and structural formulae. The simplest types of chemical formulae are called '' empirical formulae'', which use letters and numbers indicating the numerical ''proportions'' of atoms of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lanthanum
Lanthanum is a chemical element; it has symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table, of which lanthanum is the first and the prototype. Lanthanum is traditionally counted among the rare earth elements. Like most other rare earth elements, its usual oxidation state is +3, although some compounds are known with an oxidation state of +2. Lanthanum has no biological role in humans but is used by some bacteria. It is not particularly toxic to humans but does show some antimicrobial activity. Lanthanum usually occurs together with cerium and the other rare earth elements. Lanthanum was first found by the Swedish chemist Carl Gustaf Mosander in 1839 as an impurity in cerium nitrate – hence the name ''lanthanum'', from the ancient Greek (), meaning 'to lie hidden'. Although ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lanthanum(III) Oxide
Lanthanum(III) oxide, also known as lanthana, chemical formula , is an inorganic compound containing the rare earth element lanthanum and oxygen. It is used in some ferroelectric materials, as a component of optical materials, and is a feedstock for certain catalysts, among other uses. Properties Lanthanum oxide is a white solid that is insoluble in water, but dissolves in acidic solutions. absorbs moisture from air, converting to lanthanum hydroxide. Lanthanum oxide has p-type semiconducting properties and a band gap of approximately 5.8 eV. Its average room temperature resistivity is 10 kΩ·cm, which decreases with an increase in temperature. has the lowest lattice energy of the rare earth oxides, with very high dielectric constant ε = 27. Structure At low temperatures, has an A- hexagonal crystal structure. The metal atoms are surrounded by a 7 coordinate group of atoms, the oxygen ions are in an octahedral shape around the metal atom and there is one oxygen ion above ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxidation State
In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. Conceptually, the oxidation state may be positive, negative or zero. Beside nearly-pure ionic bonding, many covalent bonds exhibit a strong ionicity, making oxidation state a useful predictor of charge. The oxidation state of an atom does not represent the "real" charge on that atom, or any other actual atomic property. This is particularly true of high oxidation states, where the ionization energy required to produce a multiply positive ion is far greater than the energies available in chemical reactions. Additionally, the oxidation states of atoms in a given compound may vary depending on Electronegativities of the elements (data page), the choice of electronegativity scale used in their calculation. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great Soviet Encyclopedia
The ''Great Soviet Encyclopedia'' (GSE; , ''BSE'') is one of the largest Russian-language encyclopedias, published in the Soviet Union from 1926 to 1990. After 2002, the encyclopedia's data was partially included into the later ''Great Russian Encyclopedia'' in an updated and revised form. The GSE claimed to be "the first Marxist–Leninist general-purpose encyclopedia". Origins The idea of the ''Great Soviet Encyclopedia'' emerged in 1923 on the initiative of Otto Schmidt, a member of the Russian Academy of Sciences. In early 1924 Schmidt worked with a group which included Mikhail Pokrovsky, (rector of the Institute of Red Professors), Nikolai Meshcheryakov (Former head of the General Directorate for the Protection of State Secrets in the Press, Glavit, the State Administration of Publishing Affairs), Valery Bryusov (poet), Veniamin Kagan (mathematician) and Konstantin Kuzminsky to draw up a proposal which was agreed to in April 1924. Also involved was Anatoly Lunacharsky, People' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetyl
In organic chemistry, an acetyl group is a functional group denoted by the chemical formula and the structure . It is sometimes represented by the symbol Ac (not to be confused with the element actinium). In IUPAC nomenclature, an acetyl group is called an ethanoyl group. An acetyl group contains a methyl group () that is single-bonded to a carbonyl (), making it an acyl group. The carbonyl center of an acyl radical has one non-bonded electron with which it forms a chemical bond to the remainder (denoted with the letter ''R'') of the molecule. The acetyl moiety is a component of many organic compounds, including acetic acid, the neurotransmitter acetylcholine, acetyl-CoA, acetylcysteine, acetaminophen (also known as paracetamol), and acetylsalicylic acid (also known as aspirin). Acetylation Acetylation is the chemical reaction known as "ethanoylation" in the IUPAC nomenclature. It depicts a reactionary process that injects an acetyl functional group into a chemical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetic Anhydride
Acetic anhydride, or ethanoic anhydride, is the chemical compound with the chemical formula, formula . Commonly abbreviated , it is one the simplest organic acid anhydride, anhydrides of a carboxylic acid and is widely used in the production of cellulose acetate as well as a reagent in organic synthesis. It is a colorless liquid that smells strongly of acetic acid, which is formed by its reaction with moisture in the air. Structure and properties Acetic anhydride, like most organic acid anhydrides, is a flexible molecule with a nonplanar structure. The C=O and C-O distances are 1.19 and 1.39 Å. The Pi bond, pi system linkage through the central oxygen offers very weak resonance stabilization compared to the dipole, dipole-dipole repulsion between the two carbonyl oxygens. The energy barriers to bond rotation between each of the optimal aplanar conformations are quite low. Production Acetic anhydride was first synthesized in 1852 by the French chemist Charles Frédéric Gerhardt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Actinium Compounds
Actinium compounds are compounds containing the element actinium (Ac). Due to actinium's intense radioactivity, only a limited number of actinium compounds are known. These include: Actinium fluoride, AcF3, Actinium(III) chloride, AcCl3, Actinium(III) bromide, AcBr3, AcOF, AcOCl, AcOBr, Actinium(III) sulfide, Ac2S3, Actinium oxide, Ac2O3, Actinium(III) phosphate, AcPO4 and Actinium(III) nitrate, Ac(NO3)3. Except for AcPO4, they are all similar to the corresponding lanthanum compounds. They all contain actinium in the oxidation state +3.Actinium Great Soviet Encyclopedia (in Russian) In particular, the lattice constants of the analogous lanthanum and actinium compounds differ by only a few percent. Properties of actinium compounds Here ''a'', ''b'' and ''c'' are lattice constants, No is ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
