Metallic hydrogen is unusual as the element itself is not an alkali metal, but a diatomic gas.

Under ordinary conditions on Earth, elemental hydrogen exists as the diatomic gas, H2 (for data see table).

Fluorine is a light yellow diatomic gas.

It is stable only as a diatomic gas and has been found naturally in cool stars.

The assumption of spherical particles is necessary so that there are no rotational modes allowed, unlike in a diatomic gas.

In the transportation or detection of diatomic gases, the gas binds to the heme iron.

As temperatures rise, all diatomic gases approach this value.

Although oxygen is normally a diatomic gas, oxygen can form an allotrope known as ozone.

Hydrogen, oxygen and nitrogen are examples of dissolved diatomic gases of frequent interest in metallurgy.

This confines us to elemental monatomic or diatomic gasses.