Uranous
Encyclopedia
Uranous is the chemical term for the reduced
tetrapositive cation of uranium
that exhibits the valence U4+. It is one of the two common ionic states of uranium found in nature, the other being the oxidised
hexapositive ion called uranyl
. Uranous compounds are usually unstable; they revert to the oxidised form on exposure to air.
Examples of these compounds include uranium tetrachloride
(UCl4) and uranium tetrafluoride
(UF4), which are important in molten salt reactor
applications, and uranium dioxide
(UO2), a common form of nuclear fuel
.
The solvated U4+ ion is normally not present in water. Most of the compounds like UCl4 are better described with the covalent bond
than an ionic bond
.
Minerals containing the uranous ion
are more subdued in colour, typically brown or black, and occur in reducing environments. Common uranous minerals include: uraninite
; pitchblende (a crystalline variant of uraninite); and coffinite
(Smith,Hutchinson and Blackwell, 1984)
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
tetrapositive cation of uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
that exhibits the valence U4+. It is one of the two common ionic states of uranium found in nature, the other being the oxidised
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
hexapositive ion called uranyl
Uranyl
The uranyl ion is an oxycation of uranium in the oxidation state +6, with the chemical formula [UO2]2+. It has a linear structure with short U-O bonds, indicative of the presence of multiple bonds between uranium and oxygen. Four or more ligands are bound to the uranyl ion in an equatorial plane...
. Uranous compounds are usually unstable; they revert to the oxidised form on exposure to air.
Examples of these compounds include uranium tetrachloride
Uranium tetrachloride
Uranium tetrachloride is compound of uranium in oxidation state +4. It was used in the electromagnetic isotope separation process of uranium enrichment. It is one of the main starting materials for organouranium chemistry.- Synthesis :...
(UCl4) and uranium tetrafluoride
Uranium tetrafluoride
Uranium tetrafluoride is a green crystalline solid compound of uranium with an insignificant vapor pressure and very slight solubility in water. Uranium in its tetravalent state is very important in different technological processes...
(UF4), which are important in molten salt reactor
Molten salt reactor
A molten salt reactor is a type of nuclear fission reactor in which the primary coolant, or even the fuel itself is a molten salt mixture...
applications, and uranium dioxide
Uranium dioxide
Uranium dioxide or uranium oxide , also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used...
(UO2), a common form of nuclear fuel
Nuclear fuel
Nuclear fuel is a material that can be 'consumed' by fission or fusion to derive nuclear energy. Nuclear fuels are the most dense sources of energy available...
.
The solvated U4+ ion is normally not present in water. Most of the compounds like UCl4 are better described with the covalent bond
Covalent bond
A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding....
than an ionic bond
Ionic bond
An ionic bond is a type of chemical bond formed through an electrostatic attraction between two oppositely charged ions. Ionic bonds are formed between a cation, which is usually a metal, and an anion, which is usually a nonmetal. Pure ionic bonding cannot exist: all ionic compounds have some...
.
Minerals containing the uranous ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
are more subdued in colour, typically brown or black, and occur in reducing environments. Common uranous minerals include: uraninite
Uraninite
Uraninite is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2, but also contains UO3 and oxides of lead, thorium, and rare earth elements...
; pitchblende (a crystalline variant of uraninite); and coffinite
Coffinite
Coffinite is a uranium-bearing silicate mineral with formula: U1-x4x.It occurs as black incrustations, dark to pale-brown in thin section. It has a grayish black streak. It has a brittle to conchoidal fracture. The hardness of coffinite is between 5 and 6.It was first described in 1954 for an...
(Smith,Hutchinson and Blackwell, 1984)