Osmium (Os)
Transition metal · d-block · period 6 · group 8
Hard, brittle, bluish-white, extremely dense metal.
Osmium (symbol Os) is chemical element number 76, a transition metal in group 8, period 6 of the periodic table. Its standard atomic weight is 190.23 and its electron configuration is [Xe] 4f14 5d6 6s2. At room temperature it is a solid. The densest naturally occurring element — a football-sized lump would weigh about as much as a person on each hand... actually far more.
Properties
| Atomic number | 76 |
|---|---|
| Atomic mass | 190.23 |
| Category | Transition metal |
| Block | d-block |
| Group · Period | 8 · 6 |
| Electron configuration | [Xe] 4f14 5d6 6s2 |
| Electrons per shell | 2, 8, 18, 32, 14, 2 |
| State at 25 °C | solid |
| Melting point | 3306 K |
| Boiling point | 5285 K |
| Density | 22.59 g/cm³ |
| Electronegativity (Pauling) | 2.2 |
| Radioactive | No |
| Origin | primordial |
| Discovered | 1803 · Smithson Tennant |
Key facts about Osmium
- The densest naturally occurring element — a football-sized lump would weigh about as much as a person on each hand... actually far more.
- Its name is Greek for 'smell', after the acrid odour of its toxic oxide.
- Alloyed with iridium it tips fountain pens and instrument pivots for long wear.
- Osmium tetroxide stains fat black for microscope slides.
What Osmium is used for
Extremely hard-wearing alloy tips (pen nibs, electrical contacts, pivots), catalysts, biological staining.
Where it sits in the periodic table
Osmium is in group 8, period 6, of the d-block. Its electron configuration [Xe] 4f14 5d6 6s2 means its outermost shell holds 2 electrons, which is what places it here and explains much of its chemistry. See Osmium on the interactive table →
Osmium — frequently asked questions
What is Osmium used for?
Extremely hard-wearing alloy tips (pen nibs, electrical contacts, pivots), catalysts, biological staining.
Is Osmium radioactive?
No. Osmium has at least one stable isotope and is not radioactive.
What is the electron configuration of Osmium?
Osmium has the electron configuration [Xe] 4f14 5d6 6s2, which is 2, 8, 18, 32, 14, 2 electrons per shell.
What group and period is Osmium in?
Osmium is in group 8, period 6, in the d-block. Its outer shell holds 2 electrons.
Who discovered Osmium?
Osmium was discovered in 1803 by Smithson Tennant.