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Protactinium(V) Chloride
Protactinium(V) chloride is the chemical compound composed of protactinium and chlorine with the formula PaCl5. It forms yellow monoclinic crystals and has a unique structure composed of chains of 7 coordinate, pentagonal bipyramidal, protactinium atoms sharing edges.R. P. Dodge, G. S. Smith, Q. Johnson, R. E. Elson: „The Crystal Structure of Protactinium Pentachloride“, '' Acta Crystallogr.'', 1967, ''22'', 85–89; . Protactinium(V) chloride can react with boron tribromide at high temperatures to form protactinium(V) bromide.Georg Brauer (Hrsg.), unter Mitarbeit von Marianne Baudler u. a.: ''Handbuch der Präparativen Anorganischen Chemie.'' 3., umgearbeitete Auflage. Band I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6, S. 1177. It also reacts with fluorine to form protactinium(V) fluoride at high temperatures. See also * Protactinium(IV) chloride Protactinium(IV) chloride is an inorganic compound. It is an actinide halide, composed of protactinium and chlor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monoclinic Crystal System
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic system. They form a parallelogram prism. Hence two pairs of vectors are perpendicular (meet at right angles), while the third pair makes an angle other than 90°. Bravais lattices Two monoclinic Bravais lattices exist: the primitive monoclinic and the base-centered monoclinic. For the base-centered monoclinic lattice, the primitive cell has the shape of an oblique rhombic prism;See , row mC, column Primitive, where the cell parameters are given as a1 = a2, α = β it can be constructed because the two-dimensional centered rectangular base layer can also be described with primitive rhombic axes. Note that the length a of the primitive cell below equals \frac \sqrt of the conventional cell above. Crystal classes The table below organi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorine
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidising agent: among the elements, it has the highest electron affinity and the third-highest electronegativity on the revised Pauling scale, behind only oxygen and fluorine. Chlorine played an important role in the experiments conducted by medieval alchemists, which commonly involved the heating of chloride salts like ammonium chloride ( sal ammoniac) and sodium chloride (common salt), producing various chemical substances containing chlorine such as hydrogen chloride, mercury(II) chloride (corrosive sublimate), and hydrochloric acid (in the form of ). However, the nature of free chlorine gas as a separate substance was only recognised ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protactinium Compounds
Protactinium compounds are compounds containing the element protactinium (symbol: Pa). These compounds usually have protactinium in the +5 oxidation state, although these compounds can also exist in the +2, +3 and +4 oxidation states. Properties of protactinium compounds Here ''a'', ''b'' and ''c'' are lattice constants in picometers, No is space group number and ''Z'' is the number of formula units per unit cell; ''fcc'' stands for the face-centered cubic symmetry. Density was not measured directly but calculated from the lattice parameters. Oxides and oxygen-containing salts Protactinium oxides are known for the metal oxidation states +2, +4 and +5. The most stable is white pentoxide Pa2O5, which can be produced by igniting protactinium(V) hydroxide in air at a temperature of 500 °C.Greenwood, p. 1268 Its crystal structure is cubic, and the chemical composition is often non-stoichiometric, described as PaO2.25. Another phase of this oxide with orthorhombic symmetr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protactinium(V) Fluoride
Protactinium(V) fluoride is a fluoride of protactinium with the chemical formula PaF5. Preparation Protactinium(V) fluoride can be obtained by reacting protactinium(V) oxide with bromine trifluoride or bromine pentafluoride at 600 °C: :3 Pa2O5 + 10 BrF3 (6 BrF5) -> 6 PaF5 + 5 Br2 (3 Br2 ) + 7.5 O2 It can also be obtained by reacting protactinium(V) chloride or protactinium(IV) fluoride with fluorine gas at 700 °C: :2 PaF4 + F2 -> 2 PaF5 The hydrate form of protactinium(V) fluoride can be formed by the reaction of protactinium(V) oxide and hydrofluoric acid in an aqueous solution: :Pa2 O5 + 10 HF -> 2 PaF5 . 2 H2O + 6 H2O It can also be decomposed from fluorine-containing protactinium complexes. Properties Protactinium(V) fluoride is a white, volatile, extremely hygroscopic solid that is partially soluble in water and soluble in hydrofluoric acid. It has a tetragonal crystal structure of the β-uranium pentafluoride type with the space group ''I''42''d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorine
Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactive, as it reacts with all other elements except for the light inert gases. Among the elements, fluorine ranks 24th in universal abundance and 13th in terrestrial abundance. Fluorite, the primary mineral source of fluorine which gave the element its name, was first described in 1529; as it was added to metal ores to lower their melting points for smelting, the Latin verb meaning 'flow' gave the mineral its name. Proposed as an element in 1810, fluorine proved difficult and dangerous to separate from its compounds, and several early experimenters died or sustained injuries from their attempts. Only in 1886 did French chemist Henri Moissan isolate elemental fluorine using low-temperature electrolysis, a process still employed for moder ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marianne Baudler
Marianne Baudler (27 April 1921 – 5 March 2003) was a German chemist. She is known for her research on phosphorus. Life Marianne Baudler was born in Stettin. She started studying Chemistry at the TH Dresden in April 1940 and finished her studies with a Diplom in 1943. From 1943 to 1946, she worked on her dissertation in the group of Franz Fehér Franz may refer to: People * Franz (given name) * Franz (surname) Places * Franz (crater), a lunar crater * Franz, Ontario, a railway junction and unorganized town in Canada * Franz Lake, in the state of Washington, United States – see ... at the University of Göttingen. Starting in 1949, Baudler performed research at the University of Cologne. In 1952, she finished her habilitation. In 1963 she became extraordinary professor at the University of Cologne. In 1968, the full professorship followed. From 1986 on, she was an emeritus professor. Research Her research focused on: * Small-ring phosphorus compounds * Phosp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Georg Brauer
Georg Karl Brauer (born 11. April 1908 in Bochum, died 26. February 2001 in Freiburg im Breisgau) was a German chemist. Life Brauer was the son of the chemist Eberhard Brauer and Elisabeth Brauer, a daughter of Wilhelm Ostwald. From 1926 to 1932, Brauer studied in Leipzig and Freiburg. He received his doctorate under supervision of Eduard Zintl in Freiburg in 1933. In 1941, he received is habilitation at the TH Darmstadt. In 1946, he became an extraordinary professor in Freiburg. From 1959 to 1976, he was a full professor. Starting in 1976, he was a emeritus professor. Research Brauer's research included the chemistry and crystal chemistry of intermetallic compounds and alloys. He investigated binary systems of transition metals, in particular of oxides, nitrides, carbides, and hydrides of niobium, tantalum, and vanadium. His research also focused on oxides of rare-earth metals. Many new compounds and several new structure types (Li3N, Li3Bi, Al3Zr, ThSi2, NbO) were discover ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protactinium(V) Bromide
Protactinium(V) bromide is an inorganic compound. It is a halide of protactinium, consisting of protactinium and bromine. It is radioactive and has a chemical formula of PaBr5, which is a red crystal of the monoclinic crystal system. Preparation Protactinium(V) bromide can be obtained by reacting protactinium(V) chloride with boron tribromide at 500 to 550 °C.Georg Brauer (Hrsg.), unter Mitarbeit von Marianne Baudler u. a.: ''Handbuch der Präparativen Anorganischen Chemie.'' 3., umgearbeitete Auflage. Band I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6, S. 1177. :3PaCl5 + 5BBr3 → 3PaBr5 + 5BCl3 It can also be obtained by reacting protactinium(V) oxide with aluminum bromide at 400 °C. Physical properties Protactinium(V) bromide is an orange-red, crystalline, extremely moisture-sensitive solid that reacts violently with water and ammonia, but is persistent in absolutely dry air. It is insoluble in isopentane, dichloromethane and benzene, and in anhyd ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boron Tribromide
Boron tribromide, BBr3, is a colorless, fuming liquid compound containing boron and bromine. Commercial samples usually are amber to red/brown, due to weak bromine contamination. It is decomposed by water and alcohols. Chemical properties Boron tribromide is commercially available and is a strong Lewis acid. It is an excellent demethylating or dealkylating agent for the cleavage of ethers, also with subsequent cyclization, often in the production of pharmaceuticals. The mechanism of dealkylation of tertiary alkyl ethers proceeds via the formation of a complex between the boron center and the ether oxygen followed by the elimination of an alkyl bromide to yield a dibromo(organo) borane. :ROR + BBr3 → RO+(−BBr3)R → ROBBr2 + RBr Aryl methyl ethers (as well as activated primary alkyl ethers), on the other hand are dealkylated through a bimolecular mechanism involving two BBr3-ether adducts. :RO+(−BBr3)CH3 + RO+(−BBr3)CH3→ RO(−BBr3) + CH3Br + RO+(BBr2)CH3 The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acta Crystallogr
''Acta Crystallographica'' is a series of peer-reviewed scientific journals, with articles centred on crystallography, published by the International Union of Crystallography (IUCr). Originally established in 1948 as a single journal called ''Acta Crystallographica'', there are now six independent ''Acta Crystallographica'' titles: *'' Acta Crystallographica Section A: Foundations and Advances'' *'' Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials'' *'' Acta Crystallographica Section C: Structural Chemistry'' *'' Acta Crystallographica Section D: Structural Biology'' *'' Acta Crystallographica Section E: Crystallographic Communications'' *'' Acta Crystallographica Section F: Structural Biology Communications'' ''Acta Crystallographica'' has been noted for the high quality of the papers that it produces, as well as the large impact that its papers have had on the field of crystallography. The current six journals form part of the journal portf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Formula
In chemistry, 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, and it contains no 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 ato ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protactinium
Protactinium (formerly protoactinium) is a chemical element with the Symbol (chemistry), symbol Pa and atomic number 91. It is a dense, silvery-gray actinide metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds in which protactinium is usually present in the oxidation state +5, but it can also assume +4 and even +3 or +2 states. Concentrations of protactinium in the Earth's crust are typically a few parts per trillion, but may reach up to a few parts per million in some uraninite ore deposits. Because of its scarcity, high radioactivity and high toxicity, there are currently no uses for protactinium outside scientific research, and for this purpose, protactinium is mostly extracted from spent nuclear fuel. The element was first identified in 1913 by Kazimierz Fajans and Oswald Helmuth Göhring and named ''brevium'' because of the short half-life of the specific isotope studied, i.e. protactinium-234. A more stable isotope of p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
