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Osmium

Element 76 · Transition metal

Specimen

Atomic number
76
Atomic mass
190.23
State at room temperature
Solid
Melting point
3,033 °C
Boiling point
5,012 °C
Density
22.57 g/cm³
Discovered
1803

Atomic mass from IUPAC.1 Other physical data from PubChem.2

Can I eat it?

In food and water
Harmful. Osmium metal is not toxic. Its oxide, osmium tetroxide, is volatile and very toxic. Its vapor damages the eyes, skin and lungs, and high amounts can kill. 34

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The atom

Os
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) 18
4 (N) 32
5 (O) 14
6 (P) outermost 2
Total76

Configuration [Xe] 4f¹⁴ 5d⁶ 6s²

4f ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓
5d ↑ ↓ ↑ ↑ ↑ ↑
6s ↑ ↓
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 76 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the Xe core, with one arrow per electron.

Related elements

Group 8
Fe Iron Ru Ruthenium Hs Hassium

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Sources

  1. 1

    IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), 2024. Abridged Standard Atomic Weights 2024 .

    The atomic mass shown for the 84 elements that have a standard atomic weight.

  2. 2

    National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

    Electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  3. 3

    Royal Society of Chemistry, Periodic Table, 2026. Osmium - Element information, properties and uses .

    Reference page; its Biological role and Natural abundance sections are quoted.

    • Osmium has no known biological role. The metal is not toxic, but its oxide is volatile and very toxic, causing lung, skin and eye damage.
  4. 4

    International Labour Organization and World Health Organization (International Chemical Safety Cards), 2021. ICSC 0528 - Osmium tetroxide , Short-term exposure effects.

    • The substance is corrosive to the eyes, skin and respiratory tract. Inhalation may cause lung oedema. See Notes. Exposure to high concentrations could cause death.
  5. 5

    National Institute of Standards and Technology (NIST), 2026. Atomic Weights and Isotopic Compositions for All Elements .

    Isotopic composition of each element; the most abundant isotope sets the neutron count in the nucleus view.