Uranium (U)
Actinide · f-block · period 7
Dense, hard, silvery-grey metal that tarnishes to a dark oxide.
Uranium (symbol U) is chemical element number 92, a actinide in the actinide series (f-block), period 7 of the periodic table. Its standard atomic weight is 238.03 and its electron configuration is [Rn] 5f3 6d1 7s2. At room temperature it is a solid, and it is radioactive. Named after the planet Uranus, discovered eight years earlier.
Properties
| Atomic number | 92 |
|---|---|
| Atomic mass | 238.03 |
| Category | Actinide |
| Block | f-block |
| Group · Period | f-block series · 7 |
| Electron configuration | [Rn] 5f3 6d1 7s2 |
| Electrons per shell | 2, 8, 18, 32, 21, 9, 2 |
| State at 25 °C | solid |
| Melting point | 1405.3 K |
| Boiling point | 4404 K |
| Density | 19.1 g/cm³ |
| Electronegativity (Pauling) | 1.38 |
| Radioactive | Yes — no stable isotope |
| Origin | primordial |
| Discovered | 1789 · Martin Heinrich Klaproth |
Key facts about Uranium
- Named after the planet Uranus, discovered eight years earlier.
- The heaviest element found in any significant amount in nature.
- The isotope uranium-235 sustains the chain reaction in reactors and in the first atomic bombs.
- About two billion years ago, a uranium deposit in Gabon ran as a natural nuclear reactor.
What Uranium is used for
Nuclear reactor fuel and weapons, dense counterweights and armour (depleted uranium), historically yellow-green glass and ceramic glaze.
Where it sits in the periodic table
Uranium is in the actinide series, period 7, of the f-block. Its electron configuration [Rn] 5f3 6d1 7s2 means its outermost shell holds 2 electrons, which is what places it here and explains much of its chemistry. See Uranium on the interactive table →
Uranium — frequently asked questions
What is Uranium used for?
Nuclear reactor fuel and weapons, dense counterweights and armour (depleted uranium), historically yellow-green glass and ceramic glaze.
Is Uranium radioactive?
Yes. Uranium has no stable isotope, so every form of it is radioactive.
What is the electron configuration of Uranium?
Uranium has the electron configuration [Rn] 5f3 6d1 7s2, which is 2, 8, 18, 32, 21, 9, 2 electrons per shell.
What group and period is Uranium in?
Uranium is in the actinide series (f-block), period 7, in the f-block. Its outer shell holds 2 electrons.
Who discovered Uranium?
Uranium was discovered in 1789 by Martin Heinrich Klaproth.