Quick answerUranium (U) is an actinide with atomic number 92 and an atomic mass of 238.03 (2023), in period 7. It was discovered by Martin Heinrich Klaproth in 1789. It is used for nuclear power generation and nuclear weapons. Its electron configuration is [Rn] 5f3 6d1 7s2.
Uranium is the heaviest naturally occurring element, and the fuel of nuclear power stations and atomic weapons. A single kilogram of uranium-235 releases as much energy as burning about 2,700 tonnes of coal, which is why nuclear plants can run for years on a small load of fuel. It also colours glass and glazes yellow-green, and its slow decay lets geologists date the oldest rocks on Earth.
Key facts
| Symbol | U |
|---|---|
| Atomic number | 92 |
| Atomic mass | 238.03 (IUPAC standard atomic weight, 2023) |
| Category | actinide |
| Group | — (f-block element, no group number) |
| Period | 7 |
| Block | f-block |
| Electron configuration | [Rn] 5f3 6d1 7s2 |
| Discovered | Martin Heinrich Klaproth, 1789 |
| Uses | nuclear power generation, nuclear weapons, dating ancient rocks, colouring glass and ceramics, medical isotope production |
Overview
Uranium is the heaviest naturally occurring element, and the fuel of nuclear power stations and atomic weapons. It has atomic number 92, an atomic mass of 238.03, and the electron configuration [Rn] 5f3 6d1 7s2, and it sits in period 7, in the f-block, with no group number. Martin Heinrich Klaproth discovered it in 1789 in pitchblende ore, and named it after Uranus, the planet discovered eight years earlier. Uranium's power comes from fission: when a uranium-235 nucleus splits, it releases a huge amount of energy, and a single kilogram of uranium-235 releases as much energy as burning about 2,700 tonnes of coal, which is why nuclear plants can run for years on a small load of fuel. Uranium-235 is rare, less than 1% of natural uranium, so fuel must be enriched before use. Uranium also colours glass and ceramic glazes yellow-green, and its slow, steady decay lets geologists date the oldest rocks on Earth. Its waste stays radioactive for thousands of years, which is why storing it safely is one of the great challenges of nuclear power.
Frequently asked questions
What is uranium used for?
Uranium is mainly used as fuel for nuclear power stations, where fission of uranium-235 releases huge amounts of energy, and it was also used in atomic weapons. It colours glass and ceramic glazes yellow-green, and its slow decay lets geologists date the oldest rocks. Its waste stays radioactive for thousands of years, so safe storage matters.
What is the symbol for uranium?
The chemical symbol for uranium is U, from its name, which comes from Uranus, the planet discovered eight years earlier. Martin Heinrich Klaproth discovered it in 1789 in pitchblende ore. Uranium has atomic number 92 and a standard atomic mass of 238.03, and it is the heaviest naturally occurring element.
What is the atomic number of uranium?
Uranium has atomic number 92, so it is the ninety-second element in the periodic table. Its atom holds ninety-two protons and ninety-two electrons, and its standard atomic mass is 238.03. It is an actinide in period 7, in the f-block with no group number, and its electron configuration is [Rn] 5f3 6d1 7s2.
Is uranium a metal?
Yes, uranium is a metal, an actinide in the f-block of the periodic table. It is dense, silvery-grey and weakly radioactive, and it tarnishes in air. It is the heaviest naturally occurring element, and its isotope uranium-235 is the fuel of nuclear power stations, releasing huge energy when its nucleus splits.
Where is uranium found?
Uranium is found in rocks and ores around the world, mainly in Kazakhstan, Canada and Australia, which are the biggest producers. It occurs in minerals such as pitchblende and uraninite, and in tiny amounts in soil, seawater and granite. Natural uranium is mostly uranium-238, with less than 1% uranium-235, the fissile isotope.
Quick quiz
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Keep exploring
- Periodic table — all 118 elements
- Actinium (Ac) — another actinide, atomic number 89
- Thorium (Th) — another actinide, atomic number 90
- Protactinium (Pa) — another actinide, atomic number 91
- Neptunium (Np) — another actinide, atomic number 93
- Plutonium (Pu) — another actinide, atomic number 94
- Americium (Am) — another actinide, atomic number 95
- Curium (Cm) — another actinide, atomic number 96
- Berkelium (Bk) — another actinide, atomic number 97
- Californium (Cf) — another actinide, atomic number 98
- Einsteinium (Es) — another actinide, atomic number 99
- All actinide elements — on the periodic table
Sources & last updated
- CIAAW — Standard Atomic Weights
- PubChem Periodic Table
- Wikipedia — Timeline of chemical element discoveries
Last updated: . Figures are shown with their year; where sources disagree, the value is left out rather than estimated.