Chemical elements
    Physical Properties
    Chemical Properties
      Uranium Difluoride
      Uranium Tetrafluoride
      Uranous Oxyfluoride
      Uranium Hexafluoride
      Uranyl Fluoride
      Uranium Trichloride
      Uranium Tetrachloride
      Uranium Pentachloride
      Uranyl Chloride
      Uranyl Chlorate
      Uranyl Perchlorate
      Uranium Tetrabromide
      Uranyl Bromide
      Uranium Tetra-iodide
      Uranyl Iodide
      Uranyl Iodate
      Uranous Oxide
      Uranous Hydroxide
      Uranium Pentoxide
      Urano-uranic Oxide
      Uranium Trioxide
      Ammonium Diuranate
      Ammonium Hexa-uranate
      Hydroxylamine Uranate
      Hydroxylamine Potassio-uranate
      Barium Uranate
      Barium Diuranate
      Bismuth Uranate
      Iron Uranate
      Lithium Uranate
      Potassium Uranate
      Potassium Diuranate
      Potassium Tetra-uranate
      Potassium Hexa-uranate
      Rubidium Uranate
      Silver Diuranate
      Sodium Uranate
      Sodium Diuranate
      Sodium Triuranate
      Sodium Penta-uranate
      Strontium Uranate
      Zinc Uranate
      Peruranic acid
      Ammonium Peruranate
      Barium Peruranates
      Lithium Peruranate
      Nickel Peruranate
      Potassium Peruranate
      Sodium Peruranates
      Uranium Monosulphide
      Uranium Sesquisulphide
      Uranium Disulphide
      Uranium Oxysulphide
      Uranyl Sulphide
      Uranium Sulphite
      Uranyl Sulphite
      Complex Uranyl Sulphites
      Uranium Sulphate
      Uranium Dithionates
      Uranyl Sulphate
      Uranyl Pyrosulphate
      Uranyl Thiosulphate
      Uranyl Dithionate
      Uranium Sesquiselenide
      Uranium Diselenide
      Uranyl Selenide
      Uranyl Selenite
      Uranyl Selenate
      Uranium Telluride
      Uranium Nitrides
      Uranous Nitrate
      Uranyl Nitrate
      Uranium Monophosphide
      Uranous Phosphide
      Uranyl Hypophosphite
      Uranyl Phosphite
      Uranous Phosphates
      Uranyl Phosphates
      Complex Uranyl Phosphates
      Uranyl Aminophosphates
      Uranous Arsenide
      Uranyl Metarsenite
      Uranous Arsenate
      Uranyl Arsenates
      Complex Uranyl Arsenates
      Uranous Antimonide
      Uranous Antimonate
      Uranium Carbide
      Complex Uranyl Carbonates
      Ammonium Uranyl Carbonate
      Calcium Uranyl Carbonate
      Potassium Uranyl Carbonate
      Sodium Uranyl Carbonate
      Thallium Uranyl Carbonate
      Potassium Uranyl Ferrocyanide
      Uranyl Platinocyanide
      Uranyl Cyanate
      Uranyl Thiocyanate
      Uranium Silicide
      Uranium Boride
      Uranyl Perborate
    PDB 1anv-3pu4

Uranium Compounds

Uranium is the terminal member of the chromium group of elements, and in its chemical behaviour it shows considerable resemblance to the other members of the group. Like them Uranium in Uranium Compounds valency varying from 2 to 6, but it is most stable in the hexavalent condition. The trioxide, UO3, like the trioxides of molybdenum and tungsten, is amphoteric, but the acidic qualities are less evident. It forms on the one hand a hexafluoride, UF6, and a large group of uranyl salts of the type UO2X2, where X is a monovalent electronegative element or radical; and on the other, stable uranates corresponding to acids of composition H2UO4 and H2U2O7. It does not, however, tend to the formation of complex heteropolyacids in any marked degree. The uranyl salts, which contain the uranyl group UO2 as a divalent metallic radical, may be regarded as stable intermediate products of the hydrolytic decomposition of the normal salts of hexavalent uranium. They are well-defined crystalline salts, generally yellow, although the presence of certain organic groups in the molecule may displace the colour strongly towards the red; both in the crystalline form and in solution they exhibit a greenish fluorescence. They are somewhat analogous to basic salts, but are stable in solution and little hydrolysed. They enter into combination with other salts, especially those of organic acids, and form numerous stable complexes of well-defined crystalline form. Of the normal uranic salts only the hexafluoride is known.

The uranous compounds correspond to the basic oxide, UO2, and are usually green or blue in colour. They may be prepared by reduction of uranyl salts in solution under the influence of light (see below), but they are the more unstable and the solutions are readily oxidised back by air to uranyl compounds, especially in the presence of platinum black or of salts of iron or copper. In the uranous compounds uranium shows considerable chemical similarity to thorium, the terminal member of Group IV.

The intermediate oxide, U3O8, which appears to contain both tetra- and hexa-valent uranium, does not yield a corresponding series of salts. A large number of violet precipitates have, however, been obtained from solutions containing uranous and uranic salts present together, all of which, by loss of their acid radical, tend to become transformed into the green hydrated oxide, U3O8.2H2O.

In addition to the derivatives of the oxides, UO2 and UO3, uranium forms a few compounds in which it appears to exhibit valencies equal to 5, 3, and possibly 2. It yields, for example, a comparatively stable pentachloride, UCl5, and a much less stable trichloride, UCl3. It produces a variety of sulphides: US, U2S3, US2, UO2S, but it does not show the tendency found in molybdenum and tungsten to form soluble sulpho-salts.

It forms a peracid, UO4.2H2O, which shows considerable activity towards metallic peroxides, with the production of a well-defined series of peruranates.

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