94
Pu
Plutonium
244
Plutonium (Pu)
ActinidePeriod 7f-block-blockRadioactive
Plutonium is a transuranic radioactive chemical element with symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states.
Latin name: Plutonium
Atomic Number
94
Atomic Mass
244 g/mol
Phase (STP)
Solid
Electron Config.
[Rn] 5f⁶ 7s²
General
SymbolPu
Atomic Number94
Atomic Mass244 g/mol
CategoryActinide
Period7
Blockf-block
Electron Configuration[Rn] 5f⁶ 7s²
Valence Electrons8
Coloursilvery-gray metallic (radioactive)
Appearancesilvery white, tarnishing to dark gray in air
CAS NumberCAS7440-07-5
Physical Properties
Phase (STP)Solid
Density19.84 g/cm³
Melting Point639.35°C · 1182.83°F · 912.50 K
Boiling Point3231.85°C · 5849.33°F · 3505.00 K
Atomic Properties
Atomic Radius243 pm
Electronegativity1.28 Pauling
Ionization Energy584 kJ/mol
Oxidation States+7, +6, +5, +4, +3, +2
Ion ChargePu2+/Pu3+/Pu4+/Pu5+/Pu6+/Pu7+
Thermodynamic
Molar Heat35.5 J/(mol·K)
Crystal Structure
Crystal Structuremonoclinic (α-Pu) - complex allotropes
Nuclear & Hazards
RadioactiveYes
Half-life8.13×10^7 years (Pu-244)
Abundance
In Universe0.000000000001%
In Earth's Crust0.00000000001%
Discovery & History
Discovery Year1940
Discovered ByGlenn T. Seaborg, Edwin McMillan, Joseph W. Kennedy, Arthur C. Wahl
Country of DiscoveryUSA
Isotopes of Plutonium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Pu-238 | — | 87.7 years | α |
| Pu-239 | — | 2.411 × 10⁴ years | α |
| Pu-240 | — | 6561 years | α |
| Pu-241 | — | 14.35 years | β⁻ |
| Pu-242 | — | 3.75 × 10⁵ years | α |
| Pu-244 | — | 8.0 × 10⁷ years | α |