#76 / 118
76Os190.23
Transition Metalssolid at STPD-block

Osmium

Group: 8Period: 6Standard Atomic Weight: 190.23 u

Why is Osmium in this position?

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

Group Assignment
Group 8

Belongs to Group 8 because it has 8 valence electrons (5d⁶ 6s²).

Period Assignment
Period 6

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

Orbital Block
D-block

Belongs to the d-block because its differentiating electrons occupy 5d orbitals.

Chemical Category
Transition Metals

Classified as a transition metal and the densest platinum group metal.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 18, 32, 14, 2]

Bohr Atomic Shell Model(2, 8, 18, 32, 14, 2)

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

76 Protons (p⁺)114 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 14Shell O: Electron 2 of 14Shell O: Electron 3 of 14Shell O: Electron 4 of 14Shell O: Electron 5 of 14Shell O: Electron 6 of 14Shell O: Electron 7 of 14Shell O: Electron 8 of 14Shell O: Electron 9 of 14Shell O: Electron 10 of 14Shell O: Electron 11 of 14Shell O: Electron 12 of 14Shell O: Electron 13 of 14Shell O: Electron 14 of 14PShell P: Electron 1 of 2Shell P: Electron 2 of 2OsZ = 76

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):14 / 50 electrons (28%)
Shell P (n=6):2 / 72 electrons (3%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d⁶ 6s²

Neutral ground state configuration. Valence electrons: 8.

Atomic & Quantum Properties

Electronegativity (Pauling)2.2 Pauling
1st Ionization Energy840 kJ/mol
Electron Affinity-106.1 kJ/mol
Atomic Radius (empirical)185 pm
Common Oxidation States+4, +8
Crystal StructureHCP

Physical & Thermal Properties

Density at STP22.59 g/cm³
Melting Point3033 °C (3306 K)
Boiling Point5012 °C (5285 K)
Magnetic OrderingParamagnetic
Discovery Year1803
Discovered BySmithson Tennant

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Wear-resistant fountain pen tipping nibs and high-durability instrument pivots
  • Biological lipid tissue staining for transmission electron microscopy (OsO₄)
  • High-stress electrical relay switch contacts and pacemaker components
  • Synchrotron radiation X-ray mirrors
Occurrence in Nature

Occurs naturally as native alloys with iridium (osmiridium) and in platinum ore refinement residues.

Etymology & Name Origin

From Greek 'osme' meaning smell, due to the sharp, suffocating odor of its volatile tetroxide

Important Chemical Compounds
OsO₄ (Osmium tetroxide)
OsCl₃ (Osmium trichloride)
OsF₆ (Osmium hexafluoride)
Interesting Chemical Facts
  • Osmium is the densest substance naturally found on Earth: a single cubic foot of osmium weighs 640 kg (1,410 pounds).
  • Osmium achieves a rare +8 oxidation state in Osmium tetroxide (OsO₄), a volatile crystal that boils into a suffocating, lethal vapor at just 130 °C.
  • Osmium is so hard and brittle that it cannot be cut or machined with conventional tools, requiring electrical discharge machining (EDM).
Safety & Handling Note

Osmium tetroxide (OsO₄) is a lethal, volatile lung toxin that rapidly blinds by staining cornea tissue black.