Osmium Tetroxide OsO₄

Osmium tetroxide (OsO₄) is tetrahedral. The colourless solid is usually contaminated by a small amount of osmium dioxide (OsO₂), which is yellow-brown in colour. In 2004, a plot to detonate a bomb, believed to contain osmium tetroxide, was foiled by British intelligence sources. Although osmium tetroxide is highly toxic, the high cost (around £100/g at the time) and high reactivity (it is likely to be destroyed in an explosion) made it a very unlikely substance for the bomb makers to use.