#71 / 118
71Lu174.97
Lanthanides (Rare Earths)solid at STPD-block

Lutetium

Group: f-blockPeriod: 6Standard Atomic Weight: 174.97 u

Why is Lutetium in this position?

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

Group Assignment
Group Lanthanide / Actinide

Final member of the Lanthanide series, bridging the 4f shell into the 5d transition metals (Group 3).

Period Assignment
Period 6

Belongs to Period 6 because its outermost electrons occupy n=6.

Orbital Block
D-block

Electronically a d-block element ([Xe] 4f¹⁴ 5d¹ 6s²), marking the complete filling of the 4f subshell.

Chemical Category
Lanthanides (Rare Earths)

Classified as a lanthanide rare earth metal.

Atomic Structure & Bohr Shell Model

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

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

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

71 Protons (p⁺)104 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 9Shell O: Electron 2 of 9Shell O: Electron 3 of 9Shell O: Electron 4 of 9Shell O: Electron 5 of 9Shell O: Electron 6 of 9Shell O: Electron 7 of 9Shell O: Electron 8 of 9Shell O: Electron 9 of 9PShell P: Electron 1 of 2Shell P: Electron 2 of 2LuZ = 71

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):9 / 50 electrons (18%)
Shell P (n=6):2 / 72 electrons (3%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹ 6s²

Neutral ground state configuration. Valence electrons: 3.

Atomic & Quantum Properties

Electronegativity (Pauling)1.27 Pauling
1st Ionization Energy523.5 kJ/mol
Electron Affinity-50 kJ/mol
Atomic Radius (empirical)175 pm
Common Oxidation States+3
Crystal StructureHCP

Physical & Thermal Properties

Density at STP9.84 g/cm³
Melting Point1663 °C (1936 K)
Boiling Point3402 °C (3675 K)
Magnetic OrderingParamagnetic
Discovery Year1907
Discovered ByGeorges Urbain, Carl Auer von Welsbach & Charles James

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Targeted radioligand cancer therapy (Lutetium-177 / Pluvicto for metastatic prostate cancer)
  • Lutetium oxyorthosilicate (LSO) scintillation crystals in hospital PET medical imaging scanners
  • Petroleum cracking catalysts in refineries
  • High-index immersion lithography lenses for semiconductor microchips
Occurrence in Nature

Extracted in very low concentrations from monazite and xenotime ores; one of the costliest rare earths.

Etymology & Name Origin

From 'Lutetia', the ancient Roman Latin name for Paris

Important Chemical Compounds
Lu₂O₃ (Lutetia)
LSO (Lutetium oxyorthosilicate)
LuCl₃ (Lutetium chloride)
Interesting Chemical Facts
  • Due to the lanthanide contraction, lutetium has the smallest atomic radius, highest density (9.84 g/cm³), and highest hardness of all 15 lanthanide elements.
  • Lutetium-177 is a cutting-edge cancer drug: it binds directly to prostate-specific membrane antigen (PSMA) on cancer cells, zapping tumors with short-range beta radiation while sparing healthy tissue.
  • Georges Urbain discovered lutetium in Paris in 1907, naming it after the Roman name for the city of Paris.
Safety & Handling Note

Low physiological toxicity; metal powder is a combustible dust hazard.