Odd molecule is a term invented by Gilbert N. Lewis in 1916 for a molecule containing an odd number of electrons. Lewis in the Berkeley Lab Gilbert Newton Lewis (October 23, 1875-March 23, 1946) was a famous physical chemist. ... 1916 is a leap year starting on Saturday (link will take you to calendar) // Events January-February January 1 -The first successful blood transfusion using blood that had been stored and cooled. ... A molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... Properties The electron is a subatomic particle. ...

Taking the p-shell elements, such molecules are rare; they are usually colored and paramagnetic, that is, attracted by a magnet. Paramagnetism is the tendency of the atomic magnetic dipoles, due to quantum-mechanical spin, in a material that is otherwise non-magnetic to align with an external magnetic field. ... Magnetic lines of force of a bar magnet shown by iron filings on paper A magnet is an object that has a magnetic field. ...

Odd molecules are 'radicals'; see radicals. In chemistry, radicals (often refered to as free radicals) are atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ...

A fine example is nitric oxide, q.v.; nitrogen dioxide is another; chlorine dioxide is also an example, being a reddish-yellow gas. They are all fairly reactive. The chemical compound nitric oxide is a gas with chemical formula NO. It is an important signaling molecule in the body of mammals including humans, one of the few gaseous signaling molecules known. ... The chemical compound nitrogen dioxide (NO2) is a red or orange/brown gas with a characteristic sharp, biting odor. ... Chlorine dioxide (ClO2) is a reddish-yellow gas, which is one of several known oxides of chlorine. ...

When including d-shell elements, i.e., the transition metals, the concept mostly doesn't apply, and this 'odd' state is not so unusual.

References

• "The Atom and the Molecule", Gilbert N. Lewis, Journal of the American Chemical Society, volume 38 (1916), pages 762–786; received January 26, 1916.
• "Classic Papers" - online copy of 1916 paper - 2005-V-17