Chemical Properties of Uranium
Uranium like thorium belongs to the actinide series mainly represented by transuranic artificially received elements (plutonium, americium, curium etc.). However, by its chemical properties uranium has many features in common with molybdenum, tungsten and chrome. Its main chemical peculiarities are variable valency, amphoteric nature in quadrivalent state and propensity to forming a complex ion — uranyl (UO2)+2.
Most of the compounds of four-valent uranium are not soluble in water, however in oxidizing environment they decay and uranium transforms into hexavalent state. In neutral and acidic solutions hexavalent uranium mainly exists in the form of uranyl ion which forms salts well soluble in water. Fluoride of hexavalent uranium (hexafluoride) sublimes at 56оC and is used in the process of enrichment of natural uranium with U235 isotope.
Main Chemical Properties of Uranium
Uranium valency
2+, 3+, 4+, 5+, 6+
including in natural compounds: 19,6 — 21,bhu 2
including in natural compounds: 19,6 — 21,bhu 2
Ionic radius, nm
uranium 4+
uranium 5+
uranium 6+
uranium 5+
uranium 6+
>1408
4091
0,98
4091
0,98
Reaction with:
water
acids
alkalies
atmospheric oxygen
metals
acids
alkalies
atmospheric oxygen
metals
22,5
27,66
10,7
29,0 х 10-4
1,72 х 10-6
27,66
10,7
29,0 х 10-4
1,72 х 10-6