Osmium (Os)
Element 76 · Transition metal · Solid at 25 °C · Group 8, Period 6
Osmium is the densest naturally occurring element — a liter of it would weigh about 22.6 kg. Its alloys tip fountain-pen nibs and instrument pivots.
On the periodic table, osmium sits in group 8 in period 6. It is one of 38 elements classified as a transition metal, and at room temperature (25 °C) it is a solid.
Transition metals occupy the wide d-block in the middle of the table. As a family they are hard, dense, high-melting metals that conduct heat and electricity well. Their partly filled d-orbitals let many of them take several oxidation states, form vividly colored compounds, and act as catalysts — which is why so much of industry, and so much of biology, runs on this block.
Properties of osmium
| Atomic number (Z) | 76 |
|---|---|
| Symbol | Os |
| Atomic mass | 190.23 |
| Category | Transition metal |
| Group | 8 |
| Period | 6 |
| Block | d-block |
| Metal / nonmetal | Metal |
| State at 25 °C | Solid |
| Electron configuration | [Xe] 4f14 5d6 6s2 |
| Electronegativity (Pauling) | 2.2 |
| Melting point | 3,033 °C (3,306.15 K / 5,491.4 °F) |
| Boiling point | 5,012 °C (5,285.15 K / 9,053.6 °F) |
| Density | 22.59 g/cm³ |
Position in the periodic table
Osmium shares group 8 with Iron (Fe), Ruthenium (Ru), Hassium (Hs). Elements in the same group have the same number of outer electrons, so they tend to behave alike chemically — comparing them is one of the fastest ways to see periodic trends in action.
Within this dataset, it has the #1 highest measured density of the 97 elements with recorded values; its melting point is the #4 highest of the 102 elements with measured melting points.
Physical properties
Osmium melts at 3,033 °C (3,306.15 K / 5,491.4 °F) and boils at 5,012 °C (5,285.15 K / 9,053.6 °F), giving it a liquid range of about 1,979 °C at standard pressure.
Its density is 22.59 g/cm³.
See also: the interactive periodic table, how to read the periodic table, periodic trends.