Uranium

Occurrence, isolation & synthesis


Uranium is a silvery-white, lustrous metal, that is malleable and ductile. It tarnishes rapidly in air, forming a dark oxide [5].

Occurrence


In nature, uranium is found in the Earth's crust, 2.1 ppm, in minerals such as pitchblende, uraninite, carnotite, autunite, uranophane, davidite, tobernite, phosphate rock, lignite, and monazite sands and can be recovered commercially from these sources [3,5]. Uranium has no stable isotopes, but the isotopes found in nature are 234U (0.005 %, T½ = 2.46 · 105 years), 235U (0.718 %, T½ = 7.04 · 108 years) and 238U (99.275 %, T½ = 4.47 · 109 years) [5].

In pure solid form, uranium exist in the following forms:
α-form: orthorhombic crystal at < 667.8 ± 1.3 °C [5]
β-form: tetragonal crystal at 667.8 ± 1.3 to 774.9 ± 1.6 °C [5]
γ-form: body-centered cubic crystal at > 774.9 ± 1.6 °C [5]