Uranium (U)
Element 92 · Actinide · Solid at 25 °C · Period 7 (f-block)
Uranium fuels the world's nuclear power plants and is the heaviest element found in substantial quantities in nature.
On the periodic table, uranium sits in the f-block in period 7. It is one of 15 elements classified as an actinide, and at room temperature (25 °C) it is a solid.
The actinides fill the 5f orbitals in the bottom row of the table, and every one of them is radioactive. Only thorium and uranium occur on Earth in significant quantities; the rest are made in reactors or particle accelerators. Their nuclear properties — fission above all — shaped the twentieth century.
Properties of uranium
| Atomic number (Z) | 92 |
|---|---|
| Symbol | U |
| Atomic mass | 238.03 |
| Category | Actinide |
| Group | — (f-block, associated with group 3) |
| Period | 7 |
| Block | f-block |
| Metal / nonmetal | Metal |
| State at 25 °C | Solid |
| Electron configuration | [Rn] 5f3 6d1 7s2 |
| Electronegativity (Pauling) | 1.38 |
| Melting point | 1,132.2 °C (1,405.35 K / 2,069.96 °F) |
| Boiling point | 4,131 °C (4,404.15 K / 7,467.8 °F) |
| Density | 19.1 g/cm³ |
Position in the periodic table
Uranium belongs to the actinides, the detached f-block row shown beneath the main table. These elements all fit between groups 2 and 4 of period 7, and are pulled out into their own row only to keep the table a manageable width.
Within this dataset, it has the #9 highest measured density of the 97 elements with recorded values.
Physical properties
Uranium melts at 1,132.2 °C (1,405.35 K / 2,069.96 °F) and boils at 4,131 °C (4,404.15 K / 7,467.8 °F), giving it a liquid range of about 2,998.8 °C at standard pressure.
Its density is 19.1 g/cm³.
See also: the interactive periodic table, how to read the periodic table, periodic trends.