Uranium

Jai Ganesh · 2025-09-25 16:30:46

Uranium

Gist

Uranium (symbol U, atomic number 92) is a heavy, radioactive metal discovered in 1789 and named after the planet Uranus. It is used as a source of concentrated energy in nuclear power plants and for naval reactors due to its fissile Uranium-235 isotope, which releases significant heat when nuclear fission occurs. Uranium's uses also extend to radiation shielding, armor-piercing projectiles, and historically, in the creation of yellow glass for Roman artifacts.

Uranium, after enrichment, primarily serves as fuel for nuclear reactors to generate electricity and power naval ships and submarines. It is also used in the creation of nuclear weapons, although this requires a much higher enrichment level. Additionally, specific isotopes of uranium find applications in medical and industrial fields for research, treatments, and the sterilization of equipment, while depleted uranium has uses in ballast, counterweights, and as a component in radiation shielding.

Summary

Uranium is a chemical element; it has symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium radioactively decays, usually by emitting an alpha particle. The half-life of this decay varies between 159,200 and 4.5 billion years for different isotopes, making them useful for dating the age of the Earth. The most common isotopes in natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99% of uranium on Earth) and uranium-235 (which has 143 neutrons). Uranium has the highest atomic weight of the primordially occurring elements. Its density is about 70% higher than that of lead and slightly lower than that of gold or tungsten. It occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite.

Many contemporary uses of uranium exploit its unique nuclear properties. Uranium is used in nuclear power plants and nuclear weapons because it is the only naturally occurring element with a fissile isotope – uranium-235 – present in non-trace amounts. However, because of the low abundance of uranium-235 in natural uranium (which is overwhelmingly uranium-238), uranium needs to undergo enrichment so that enough uranium-235 is present. Uranium-238 is fissionable by fast neutrons and is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor. Another fissile isotope, uranium-233, can be produced from natural thorium and is studied for future industrial use in nuclear technology. Uranium-238 has a small probability for spontaneous fission or even induced fission with fast neutrons; uranium-235, and to a lesser degree uranium-233, have a much higher fission cross-section for slow neutrons. In sufficient concentration, these isotopes maintain a sustained nuclear chain reaction. This generates the heat in nuclear power reactors and produces the fissile material for nuclear weapons. The primary civilian use for uranium harnesses the heat energy to produce electricity. Depleted uranium (238U) is used in kinetic energy penetrators and armor plating.

The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after the recently discovered planet Uranus. Eugène-Melchior Péligot was the first person to isolate the metal, and its radioactive properties were discovered in 1896 by Henri Becquerel. Research by Otto Hahn, Lise Meitner, Enrico Fermi and others, such as J. Robert Oppenheimer starting in 1934 led to its use as a fuel in the nuclear power industry and in Little Boy, the first nuclear weapon used in war. An ensuing arms race during the Cold War between the United States and the Soviet Union produced tens of thousands of nuclear weapons that used uranium metal and uranium-derived plutonium-239. Dismantling of these weapons and related nuclear facilities is carried out within various nuclear disarmament programs and costs billions of dollars. Weapon-grade uranium obtained from nuclear weapons is diluted with uranium-238 and reused as fuel for nuclear reactors. Spent nuclear fuel forms radioactive waste, which mostly consists of uranium-238 and poses a significant health threat and environmental impact.

Details

Uranium (U) is a radioactive chemical element of the actinoid series of the periodic table, atomic number 92. It is an important nuclear fuel.

Uranium constitutes about two parts per million of Earth’s crust. Some important uranium minerals are pitchblende (impure U3O8), uraninite (UO2), carnotite (a potassium uranium vanadate), autunite (a calcium uranium phosphate), and torbernite (a copper uranium phosphate). These and other recoverable uranium ores, as sources of nuclear fuels, contain many times more energy than all the known recoverable deposits of fossil fuels. One pound of uranium yields as much energy as 1.4 million kilograms (3 million pounds) of coal.

For additional information about uranium ore deposits, as well as coverage of mining, refining, and recovery techniques, see uranium processing.

Uranium is a dense, hard metallic element that is silvery white in colour. It is ductile, malleable, and capable of taking a high polish. In air the metal tarnishes and when finely divided breaks into flames. It is a relatively poor conductor of electricity. Though discovered (1789) by German chemist Martin Heinrich Klaproth, who named it after the then recently discovered planet Uranus, the metal itself was first isolated (1841) by French chemist Eugène-Melchior Péligot by the reduction of uranium tetrachloride (UCl4) with potassium.

The formulation of the periodic system by Russian chemist Dmitry Mendeleyev in 1869 focused attention on uranium as the heaviest chemical element, a position that it held until the discovery of the first transuranium element neptunium in 1940. In 1896 the French physicist Henri Becquerel discovered in uranium the phenomenon of radioactivity, a term first used in 1898 by French physicists Marie and Pierre Curie. This property was later found in many other elements. It is now known that uranium, radioactive in all its isotopes, consists naturally of a mixture of uranium-238 (99.27 percent, 4,510,000,000-year half-life), uranium-235 (0.72 percent, 713,000,000-year half-life), and uranium-234 (0.006 percent, 247,000-year half-life). These long half-lives make determinations of the age of Earth possible by measuring the amounts of lead, uranium’s ultimate decay product, in certain uranium-containing rocks. Uranium-238 is the parent and uranium-234 one of the daughters in the radioactive uranium decay series; uranium-235 is the parent of the actinium decay series.

The element uranium became the subject of intense study and broad interest after German chemists Otto Hahn and Fritz Strassmann discovered in late 1938 the phenomenon of nuclear fission in uranium bombarded by slow neutrons. Italian-born American physicist Enrico Fermi suggested (early 1939) that neutrons might be among the fission products and could thus continue the fission as a chain reaction. Hungarian-born American physicist Leo Szilard, American physicist Herbert L. Anderson, French chemist Frédéric Joliot-Curie, and their coworkers confirmed (1939) this prediction; later investigation showed that an average of 2 1/2 neutrons per atom are released during fission. Those discoveries led to the first self-sustaining nuclear chain reaction (December 2, 1942), the first atomic bomb test (July 16, 1945), the first atomic bomb dropped in warfare (August 6, 1945), the first atomic-powered submarine (1955), and the first full-scale nuclear-powered electrical generator (1957).

Fission occurs with slow neutrons in the relatively rare isotope uranium-235 (the only naturally occurring fissile material), which must be separated from the plentiful isotope uranium-238 for its various uses. Uranium-238, however, after absorbing neutrons and undergoing negative beta decay, is transmuted into the synthetic element plutonium, which is fissile with slow neutrons. Natural uranium, therefore, can be used in converter and breeder reactors, in which fission is sustained by the rare uranium-235 and plutonium is manufactured at the same time by the transmutation of uranium-238. Fissile uranium-233 can be synthesized for use as a nuclear fuel from the nonfissile thorium isotope thorium-232, which is abundant in nature. Uranium is also important as the primary material from which the synthetic transuranium elements have been prepared by transmutation reactions.

Uranium, which is strongly electropositive, reacts with water; it dissolves in acids but not in alkalies. The important oxidation states are +4 and +6. In an aqueous solution uranium is most stable as the uranyl ion, which has a linear structure [O=U=O]2+. Uranium also exhibits a +3 and a +5 state, but the respective ions are unstable. The red U3+ ion oxidizes slowly even in water that contains no dissolved oxygen. The colour of the UO2+ ion is unknown because it undergoes disproportionation even in very dilute solutions.

Uranium compounds have been used as colouring agents for ceramics. Uranium hexafluoride (UF6) is a solid with an unusually high vapour pressure (115 torr = 0.15 atm = 15,300 Pa) at 25 °C (77 °F). UF6 is chemically very reactive, but, despite its corrosive nature in the vapour state, UF6 has been widely used in the gas-diffusion and gas-centrifuge methods of separating uranium-235 from uranium-238.

Organometallic compounds are an interesting and important group of compounds in which there are metal-carbon bonds linking a metal to organic groups. Uranocene is an organouranium compound U(C8H8)2, in which a uranium atom is sandwiched between two organic ring layers related to cyclooctatetraene C8H8. Its discovery in 1968 opened a new area of organometallic chemistry.

Element Properties

atomic number : 92
atomic weight : 238.03
melting point : 1,132.3 °C (2,070.1 °F)
boiling point : 3,818 °C (6,904 °F)
specific gravity : 19.05
oxidation states : +3, +4, +5, +6.

Additional Information:

Appearance

A radioactive, silvery metal.

Uses

Uranium is a very important element because it provides us with nuclear fuel used to generate electricity in nuclear power stations. It is also the major material from which other synthetic transuranium elements are made.

Naturally occurring uranium consists of 99% uranium-238 and 1% uranium-235. Uranium-235 is the only naturally occurring fissionable fuel (a fuel that can sustain a chain reaction). Uranium fuel used in nuclear reactors is enriched with uranium-235. The chain reaction is carefully controlled using neutron-absorbing materials. The heat generated by the fuel is used to create steam to turn turbines and generate electrical power.

In a breeder reactor uranium-238 captures neutrons and undergoes negative beta decay to become plutonium-239. This synthetic, fissionable element can also sustain a chain reaction.

Uranium is also used by the military to power nuclear submarines and in nuclear weapons.

Depleted uranium is uranium that has much less uranium-235 than natural uranium. It is considerably less radioactive than natural uranium. It is a dense metal that can be used as ballast for ships and counterweights for aircraft. It is also used in ammunition and armour.

Biological role

Uranium has no known biological role. It is a toxic metal.

Natural abundance

Uranium occurs naturally in several minerals such as uranite (pitchblende), brannerite and carnotite. It is also found in phosphate rock and monazite sands. World production of uranium is about 41,000 tonnes per year.

Extracted uranium is converted to the purified oxide, known as yellow-cake. Uranium metal can be prepared by reducing uranium halides with Group 1 or Group 2 metals, or by reducing uranium oxides with calcium or aluminium.

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#1 2025-09-25 16:30:46

Uranium

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