![Plutonium element card: symbol Pu, atomic number 94, atomic mass [244], electron configuration [Rn] 5f⁶ 7s², oxidation states +4, Actinide, f-block, period 7, solid at room temperature.](https://stage.chemistry-dictionary.com/wp-content/uploads/2026/09/plutonium-chemical-element.webp)
Plutonium is a highly reactive, silvery-gray metal when it is first made. It quickly turns a dull, dark color when exposed to air. You can find tiny trace amounts of it naturally in uranium ores.
This happens when natural uranium atoms capture stray neutrons. However, scientists make almost all plutonium artificially inside nuclear reactors. They do this by hitting uranium-238 with a flow of neutrons.
The solid metal has a low melting point and a very high density. Unlike most things, plutonium actually expands as it melts into a liquid. It sits in the f-block of the periodic table with other heavy radioactive elements.
Its complex electron layout causes strange behavior and unpredictable chemical bonds. It often forms compounds that lack fixed atomic ratios. The metal goes through extreme physical changes under normal temperature swings.
Metal workers must mix plutonium with the element gallium. This mixture stabilizes the metal’s structure at room temperature. This vital step lets workers safely shape the metal into strong parts.
Without the gallium, pure plutonium parts would become brittle. They would simply shatter during the manufacturing process.