Osmium is an extremely dense, hard, brittle, bluish-white transition metal. It forms a highly toxic, volatile tetroxide (OsO₄) and is used in wear-resistant contacts, fountain-pen tips, and catalysts.
The electron configuration of osmium is [Xe] 4f14 5d6 6s2. This configuration shows a fully filled 4f subshell and partially filled 5d orbitals, typical for a heavy transition metal with multiple oxidation states.
Osmium has a density of about 22.59 g/cm³, making it the densest naturally occurring element. This is due to its heavy atomic mass and very tightly packed atoms within its hexagonal close-packed (hcp) crystal structure.
Osmium exhibits a wide range of oxidation states, from −2 to +8. The most common and stable states are +4 (e.g., OsCl4) and +8 (in osmium tetroxide, OsO4). The +8 state is the highest oxidation state known for any naturally occurring element.
Osmium tetroxide (OsO4) is a volatile and highly toxic compound. It is a strong oxidizing agent used in organic chemistry and microscopy for staining biological tissues. However, it is dangerous because it can oxidize organic matter, including lung tissue and eyes, causing severe damage even at low concentrations.
\(\mathrm{Os(s) + 2\,O_2(g) \rightarrow OsO_4(s)}\)
Key applications of osmium include:
Osmium is extremely hard, corrosion-resistant, and wear-resistant. These properties make it ideal for use in precision instruments, pen nibs, and electrical contacts that require durability under repeated friction or electrical discharge.
Osmium metal slowly oxidizes in air to form osmium tetroxide (OsO4), a volatile compound with a pungent odor and extreme toxicity. Therefore, osmium is usually handled in airtight containers or inert atmospheres.
\(\mathrm{Os(s) + 2\,O_2(g) \rightarrow OsO_4(s)}\)
Osmium is one of the rarest elements in Earth’s crust, typically found alloyed with other platinum-group metals in ores such as osmiridium and iridosmine. It is obtained as a by-product of platinum and nickel refining.
Osmium is a hard, brittle, bluish-white metal with a melting point of about 3033 °C and a boiling point around 5012 °C. It has the highest density of any natural element and maintains its metallic luster even at high temperatures.
While metallic osmium is relatively stable and safe, its oxide, OsO4, is highly toxic and must be handled in well-ventilated areas or under a fume hood. Exposure can lead to severe respiratory damage, skin burns, or eye injury.
When osmium reacts with chlorine gas, it forms osmium tetrachloride (OsCl4):
\(\mathrm{Os(s) + 2\,Cl_2(g) \rightarrow OsCl_4(s)}\)
This compound is used as a precursor in osmium chemistry and catalysis research.