I. Definition of uranium
Uranium is an element with atomic number 92, and its symbol is U, which is the heaviest primary element found in nature. There are three isotopes in nature, all of which are radioactive and have a very long half-life (hundreds of thousands to 4.5 billion years).
In addition, there are 12 artificial isotopes (226U~240U). Uranium was discovered by Martin Heinrich Klaproth in 1789. In the early days, uranium compounds were used to color porcelain.
Second, the chemical properties
Uranium is a actinide radioactive chemical element of group Ⅲ B with symbol U, atomic number 92 and relative atomic mass 238.03. It is a natural element with the largest atomic number and relative atomic weight. Uranium is a silver-white dense metal at room temperature, and the new section of uranium is bright steel gray, but a black oxide film is gradually formed in the air at room temperature.
The configuration of the outer electron shell of uranium atom is [Rn]5f36d 17s2, and the shell of 5f36d 17s2 is valence electron. Uranium has four valence states: +3, +4, +5 and +6, of which +4 and +6 are the main valence states.
Distribution range and extractive metallurgy
I. Scope of distribution
Uranium is usually regarded as a rare metal. Although the content of uranium in the earth's crust is very high, much more than that of mercury, bismuth and silver, it is destined to be discovered much later than mercury because of the difficulty in extracting uranium. Although uranium is widely distributed in the earth's crust, there are only two common deposits: pitchblende and potash.
The average content of uranium in the earth's crust is about 2.5 parts per million, that is, the average content of uranium per ton of earth's crust is 2.5 grams, which is higher than that of tungsten, mercury, gold, silver and other elements. The uranium content in various rocks is very uneven.
Second, extracting metallurgy.
Uranium extraction metallurgy has three characteristics. 1. The grade of uranium ore is very low, generally containing 0. 1% ~ 0.2%(238 u+235U), of which 235 u is only 0.0007% ~ 0.00 14%. In order to obtain nuclear pure uranium, a series of concentration and purification processes are needed.
Second, nuclear pure metallic uranium needs isotope separation to make 235U enriched uranium with different abundance. Third, the process is complex and there is radiation hazard. Therefore, uranium production technology is difficult and safety protection requirements are strict.