94 Pu

Plutonium (Pu)

Element 94 · Actinide · Solid at 25 °C · Period 7 (f-block)

Plutonium, named after Pluto, powered the first nuclear weapons — and, more peacefully, the radioisotope generators aboard deep-space probes like Voyager.

On the periodic table, plutonium 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 plutonium

Properties of Plutonium
Atomic number (Z)	94
Symbol	Pu
Atomic mass	(244) (mass number of the most stable isotope; this element has no standard atomic weight)
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] 5f6 7s2
Electronegativity (Pauling)	1.28
Melting point	640 °C (913.15 K / 1,184 °F)
Boiling point	3,228 °C (3,501.15 K / 5,842.4 °F)
Density	19.816 g/cm³

Position in the periodic table

Plutonium 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 #6 highest measured density of the 97 elements with recorded values.

Physical properties

Plutonium melts at 640 °C (913.15 K / 1,184 °F) and boils at 3,228 °C (3,501.15 K / 5,842.4 °F), giving it a liquid range of about 2,588 °C at standard pressure.

Its density is 19.816 g/cm³.

Data notes

The atomic mass is shown in parentheses because this element has no standard atomic weight; the number given is the mass number of its most stable known isotope.