Plutonium (Pu)

Plutonium is a 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.

Atomic Number

94

Atomic Mass

244 u

Category

actinide

Phase

solid

Density

19.816 g/cm³

Electron Shells

2, 8, 18, 32, 24, 8, 2

Atomic Structure

Protons: 94 • Electrons: 94 • Neutrons: Varies by isotope

Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f⁶

Discovery

1940 • Glenn T. Seaborg, Arthur C. Wahl, Joseph W. Kennedy, Edwin McMillan