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94Pu[244]
Actinidessolid at STPF-block

Plutonium

Group: f-blockPeriod: 7Standard Atomic Weight: [244] u

Why is Plutonium in this position?

Understanding the scientific rationale behind Plutonium's position in the periodic table:

Group Assignment
Group Lanthanide / Actinide

Actinide series element filling the 5f subshell.

Period Assignment
Period 7

Belongs to Period 7 because its outermost electrons occupy n=7.

Orbital Block
F-block

Belongs to the f-block because valence electrons fill 5f orbitals (5f⁶ 7s²).

Chemical Category
Actinides

Classified as an actinide radioactive metal with paramount nuclear energy importance.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 18, 32, 24, 8, 2]

Bohr Atomic Shell Model(2, 8, 18, 32, 24, 8, 2)

Hover or tap any shell orbit ring to inspect electron counts and 2n² capacities.

94 Protons (p⁺)150 Neutrons (n⁰)
KShell K: Electron 1 of 2Shell K: Electron 2 of 2LShell L: Electron 1 of 8Shell L: Electron 2 of 8Shell L: Electron 3 of 8Shell L: Electron 4 of 8Shell L: Electron 5 of 8Shell L: Electron 6 of 8Shell L: Electron 7 of 8Shell L: Electron 8 of 8MShell M: Electron 1 of 18Shell M: Electron 2 of 18Shell M: Electron 3 of 18Shell M: Electron 4 of 18Shell M: Electron 5 of 18Shell M: Electron 6 of 18Shell M: Electron 7 of 18Shell M: Electron 8 of 18Shell M: Electron 9 of 18Shell M: Electron 10 of 18Shell M: Electron 11 of 18Shell M: Electron 12 of 18Shell M: Electron 13 of 18Shell M: Electron 14 of 18Shell M: Electron 15 of 18Shell M: Electron 16 of 18Shell M: Electron 17 of 18Shell M: Electron 18 of 18NShell N: Electron 1 of 32Shell N: Electron 2 of 32Shell N: Electron 3 of 32Shell N: Electron 4 of 32Shell N: Electron 5 of 32Shell N: Electron 6 of 32Shell N: Electron 7 of 32Shell N: Electron 8 of 32Shell N: Electron 9 of 32Shell N: Electron 10 of 32Shell N: Electron 11 of 32Shell N: Electron 12 of 32Shell N: Electron 13 of 32Shell N: Electron 14 of 32Shell N: Electron 15 of 32Shell N: Electron 16 of 32Shell N: Electron 17 of 32Shell N: Electron 18 of 32Shell N: Electron 19 of 32Shell N: Electron 20 of 32Shell N: Electron 21 of 32Shell N: Electron 22 of 32Shell N: Electron 23 of 32Shell N: Electron 24 of 32Shell N: Electron 25 of 32Shell N: Electron 26 of 32Shell N: Electron 27 of 32Shell N: Electron 28 of 32Shell N: Electron 29 of 32Shell N: Electron 30 of 32Shell N: Electron 31 of 32Shell N: Electron 32 of 32OShell O: Electron 1 of 24Shell O: Electron 2 of 24Shell O: Electron 3 of 24Shell O: Electron 4 of 24Shell O: Electron 5 of 24Shell O: Electron 6 of 24Shell O: Electron 7 of 24Shell O: Electron 8 of 24Shell O: Electron 9 of 24Shell O: Electron 10 of 24Shell O: Electron 11 of 24Shell O: Electron 12 of 24Shell O: Electron 13 of 24Shell O: Electron 14 of 24Shell O: Electron 15 of 24Shell O: Electron 16 of 24Shell O: Electron 17 of 24Shell O: Electron 18 of 24Shell O: Electron 19 of 24Shell O: Electron 20 of 24Shell O: Electron 21 of 24Shell O: Electron 22 of 24Shell O: Electron 23 of 24Shell O: Electron 24 of 24PShell P: Electron 1 of 8Shell P: Electron 2 of 8Shell P: Electron 3 of 8Shell P: Electron 4 of 8Shell P: Electron 5 of 8Shell P: Electron 6 of 8Shell P: Electron 7 of 8Shell P: Electron 8 of 8QShell Q: Electron 1 of 2Shell Q: Electron 2 of 2PuZ = 94

Educational Note: This Niels Bohr planetary model visually illustrates principal quantum energy shells ($n=1, 2, 3\dots$) and electron counts. In modern quantum mechanics (Schrödinger model), electrons do not orbit in fixed circular planetary tracks, but exist as 3D probability clouds (orbitals: $s, p, d, f$) governed by the Heisenberg uncertainty principle.

Electron Shell Filling Breakdown

Shell K (n=1):2 / 2 electrons (100%)
Shell L (n=2):8 / 8 electrons (100%)
Shell M (n=3):18 / 18 electrons (100%)
Shell N (n=4):32 / 32 electrons (100%)
Shell O (n=5):24 / 50 electrons (48%)
Shell P (n=6):8 / 72 electrons (11%)
Shell Q (n=7):2 / 98 electrons (2%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f⁶ 6s² 6p⁶ 7s²

Neutral ground state configuration. Valence electrons: 8.

Atomic & Quantum Properties

Electronegativity (Pauling)1.28 Pauling
1st Ionization Energy584.7 kJ/mol
Electron Affinity-48.3 kJ/mol
Atomic Radius (empirical)187 pm
Common Oxidation States+4, +3, +6
Crystal StructureMonoclinic (alpha)

Physical & Thermal Properties

Density at STP19.86 g/cm³
Melting Point639.4 °C (912.55 K)
Boiling Point3228 °C (3501 K)
Magnetic OrderingParamagnetic
Discovery Year1940
Discovered ByGlenn T. Seaborg, Edwin McMillan, Joseph W. Kennedy & Arthur Wahl

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Fissile nuclear weapons core material and mixed-oxide (MOX) commercial reactor fuel (Plutonium-239)
  • Radioisotope Thermoelectric Generators (RTGs) powering NASA Voyager 1 & 2, New Horizons, and Mars Perseverance rover (Plutonium-238)
  • Historical cardiac pacemakers providing 20-year battery-free life
Occurrence in Nature

Synthesized inside nuclear reactors by neutron capture on Uranium-238 followed by beta decay; trace primordial traces of Plutonium-244 exist in Earth's crust.

Etymology & Name Origin

Named after the dwarf planet Pluto, continuing the astronomical sequence Uranus-Neptune-Pluto

Important Chemical Compounds
PuO₂ (Plutonium dioxide)
PuF₄ (Plutonium tetrafluoride)
Pu(NO₃)₄ (Plutonium nitrate)
Interesting Chemical Facts
  • A piece of Plutonium-238 glows bright cherry-red continuously in the dark due to self-heating from radioactive alpha decay.
  • Plutonium exhibits six distinct allotropic solid crystal phases at atmospheric pressure, expanding and contracting erratically when heated.
  • The NASA Voyager 1 space probe has traveled over 24 billion kilometers into interstellar space powered entirely by Plutonium-238 RTG batteries.
Safety & Handling Note

Extremely radiotoxic alpha emitter; bone-seeking radionuclide that causes fatal bone marrow destruction and lung cancer if inhaled.