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Ruthenium

Element 44 · Transition metal

Specimen

Atomic number
44
Atomic mass
101.1
State at room temperature
Solid
Melting point
2,334 °C
Boiling point
4,150 °C
Density
12.1 g/cm³
Discovered
1827

Physical data from PubChem.1

Can I eat it?

In food and water
Not needed, little harm known. Ruthenium has no known function in the body, and few safety data exist. For impurities in medicines, ICH uses the palladium limit of 100 micrograms a day by mouth. The RSC calls ruthenium oxide highly toxic. 23

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The atom

Ru
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) 18
4 (N) 15
5 (O) outermost 1
Total44

Configuration [Kr] 4d⁷ 5s¹

4d ↑ ↓ ↑ ↓ ↑ ↑ ↑
5s ↑
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 44 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 Kr core, with one arrow per electron.

Related elements

Group 8
Fe Iron Os Osmium Hs Hassium

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Sources

  1. 1

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

    Atomic mass, electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  2. 2

    International Council for Harmonisation (ICH), 2022. ICH Q3D(R2) Guideline for Elemental Impurities .

    Limits (permitted daily exposures) for metal impurities in medicines. Used here for the platinum-group metals, which no food authority covers.

    • There are very few published data on the safety of Iridium, Osmium, Rhodium and Ruthenium. ... Pd PDE will apply to iridium, osmium, rhodium, and ruthenium.
  3. 3

    Royal Society of Chemistry, 2026. Ruthenium - Element information, properties and uses .

    • Ruthenium has no known biological role. Ruthenium(IV) oxide is highly toxic.