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93Np[237]
Actinidessolid at STPF-block

Neptunium

Group: f-block•Period: 7•Standard Atomic Weight: [237] u
Open Full Periodic TableView Bohr Model

Why is Neptunium in this position?

Understanding the scientific rationale behind Neptunium'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.

Chemical Category
Actinides

Classified as an actinide transuranic radioactive metal.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 18, 32, 22, 9, 2]

Bohr Atomic Shell Model(2, 8, 18, 32, 22, 9, 2)

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

93 Protons (p⁺)144 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 22Shell O: Electron 2 of 22Shell O: Electron 3 of 22Shell O: Electron 4 of 22Shell O: Electron 5 of 22Shell O: Electron 6 of 22Shell O: Electron 7 of 22Shell O: Electron 8 of 22Shell O: Electron 9 of 22Shell O: Electron 10 of 22Shell O: Electron 11 of 22Shell O: Electron 12 of 22Shell O: Electron 13 of 22Shell O: Electron 14 of 22Shell O: Electron 15 of 22Shell O: Electron 16 of 22Shell O: Electron 17 of 22Shell O: Electron 18 of 22Shell O: Electron 19 of 22Shell O: Electron 20 of 22Shell O: Electron 21 of 22Shell O: Electron 22 of 22PShell P: Electron 1 of 9Shell P: Electron 2 of 9Shell P: Electron 3 of 9Shell P: Electron 4 of 9Shell P: Electron 5 of 9Shell P: Electron 6 of 9Shell P: Electron 7 of 9Shell P: Electron 8 of 9Shell P: Electron 9 of 9QShell Q: Electron 1 of 2Shell Q: Electron 2 of 2NpZ = 93

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):22 / 50 electrons (44%)
Shell P (n=6):9 / 72 electrons (13%)
Shell Q (n=7):2 / 98 electrons (2%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f⁴ 6s² 6p⁶ 6d¹ 7s²

Neutral ground state configuration. Valence electrons: 7.

Atomic & Quantum Properties

Electronegativity (Pauling)1.36 Pauling
1st Ionization Energy604.5 kJ/mol
Electron Affinity-45.9 kJ/mol
Atomic Radius (empirical)190 pm
Common Oxidation States+5, +4
Crystal StructureOrthorhombic

Physical & Thermal Properties

Density at STP20.45 g/cm³
Melting Point639 °C (912 K)
Boiling Point3902 °C (4175 K)
Magnetic OrderingParamagnetic
Discovery Year1940
Discovered ByEdwin McMillan & Philip H. Abelson

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Nuclear reactor precursor for producing Plutonium-238 heat sources for NASA deep-space missions
  • High-energy neutron detection physics instruments
  • Nuclear physics and actinide chemistry research
Occurrence in Nature

Synthesized in nuclear power reactors as a byproduct of neutron capture on Uranium-235/238; trace quantities in natural uranium ores.

Etymology & Name Origin

Named after the planet Neptune, following uranium (Uranus)

Important Chemical Compounds
NpO₂ (Neptunium dioxide)
NpF₄ (Neptunium tetrafluoride)
Interesting Chemical Facts
  • • Neptunium was the first element beyond uranium ever synthesized by human science (transuranic element).
  • • Edwin McMillan won the 1951 Nobel Prize in Chemistry for discovering neptunium.
  • • Neptunium has the widest liquid temperature range of any element: an astonishing 3,263 °C between its melting and boiling points.
Safety & Handling Note

Radioactive alpha emitter and hazardous heavy metal; bioaccumulates in skeletal bones.

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