Osmium (from Greek osme (ὀσμή) meaning "smell") is a chemical element with symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mostly in platinum ores. Osmium is the densest naturally occurring element, with a density of 22.59 g/cm3.
Three reasons Osmium stands out
- 1
Densest naturally occurring element.
- 2
Its tetroxide compound has a notoriously nauseating smell — the element's very name comes from the Greek word for odour.
- 3
It is used to stain biological tissue samples for examination under a powerful electron microscope.
Density with a dangerous smell
Osmium is the densest naturally occurring element, narrowly competing with iridium depending on how density is calculated. The metal is hard and durable, but osmium tetroxide is volatile, intensely toxic, and pungent. Carefully controlled, that compound stains biological membranes for electron microscopy.