Plutonium (Pu)

Plutonium properties

Atomic number

94

Atomic mass

244 u

Category

Actinide

Group

—

Period

7

Block

f-block

State at room temp.

Solid

Electronegativity

1.28

Melting point

912.5 K (639.4 °C)

Boiling point

3,505 K (3,231.8 °C)

Density

19.82 g/cm³

Valence electrons

2

Common charges

+3, +4, +5, +6

Oxidation states

+6, +5, +4, +3

Atomic radius

243 pm

Ionization energy

6.06 eV

Electron affinity

—

Radioactive

Yes, no stable isotopes

Discovered

1940

Plutonium electron configuration

The electron configuration of Plutonium (Pu) is [Rn] 5f6 7s2. Its 94 electrons are arranged in shells as 2, 8, 18, 32, 24, 8, 2.

Protons, neutrons and electrons in Plutonium

A neutral Plutonium atom has 94 protons and 94 electrons. Most Plutonium atoms have about 150 neutrons: the atomic mass rounded to 244, minus the atomic number 94.

Neutrons are approximate: atoms of the same element can have different numbers of neutrons (isotopes). Atomic number and mass

How many valence electrons does Plutonium have?

2

Plutonium has 2 valence electrons in its outermost shell. As an f-block element, its 4f or 5f electrons can also take part in bonding.

See every element: Periodic table with valence electrons

Plutonium orbital diagram

Each box is an orbital that holds up to two electrons with opposite spins (↑↓). The inner shells are the same as the noble gas in brackets. How to write electron configurations

Molar mass of Plutonium

244 g/mol

One mole of Plutonium atoms (6.022 × 10²³ atoms) has a mass of 244 grams. Use this value to convert between grams and moles.

Plutonium facts

• Plutonium has six different crystal forms at normal pressure, and its density changes sharply as it switches between them.
• A lump of plutonium feels warm to the touch because of the energy released by its own radioactive decay.
• Plutonium (Pu) has atomic number 94 and is a solid at room temperature. It was discovered in 1940.

Position in the periodic table

Plutonium is element 94, in period 7 of the periodic table. It is one of the Actinides in the f-block, shown in the rows below the main table.

All actinides

Uses of Plutonium

Plutonium-239 is a nuclear fuel: it is used in nuclear weapons and, mixed with uranium as MOX fuel, in some nuclear power reactors. Plutonium-238 gives off steady heat as it decays, so it powers radioisotope thermoelectric generators on deep-space probes such as Voyager, Cassini and New Horizons, as well as on Mars rovers.

Who discovered Plutonium?

Glenn Seaborg, Edwin McMillan, Joseph Kennedy and Arthur Wahl first made plutonium in late 1940 at the University of California, Berkeley, by bombarding uranium with deuterons. It was named after Pluto, then considered the next planet after Neptune.

Where does the name come from?

Plutonium is named after Pluto, then considered the next planet beyond Neptune, following the pattern of uranium and neptunium. Pluto, now classed as a dwarf planet, is named after the Roman god of the underworld.

Discovery timeline