Page "Molecule" Paragraph 4

Molecules as components of matter are common in organic substances ( and therefore biochemistry ).

They also make up most of the oceans and atmosphere.

However, the majority of familiar solid substances on Earth, including most of the minerals that make up the crust, mantle, and core of the Earth, contain many chemical bonds, but are not made of identifiable molecules.

Also, no typical molecule can be defined for ionic crystals ( salts ) and covalent crystals ( network solids ), although these are often composed of repeating unit cells that extend either in a plane ( such as in graphene ) or three-dimensionally ( such as in diamond, quartz, or sodium chloride ).

The theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding, which means that solid metals are also not made of molecules.

In glasses ( solids that exist in a vitreous disordered state ), atoms may also be held together by chemical bonds without presence of any definable molecule, but also without any of the regularity of repeating units that characterises crystals.