molecule

The molecules of a compound are bound together into solids and liquids by Van der Waals forces which are very weak. Other forces also can help and the reason that water (a molecule lighter than carbon dioxide) is a liquid at room temperature is because it has a strong dipole and the bonds between the water molecules have a very strong ionic character. In fact ice is much more ionic than molecular in character.

There are other forms of material that are not molecular but are also not elemental in nature.

• ionic materials are composed of charged ions which are held together by electrostatic forces.
• metallic solids are composed of atoms which are very tightly bound by covalent style bonds. However the electrons are not isolated in individual bonds as the orbitals extend through the material. While some metals are elemental most are alloys of some form.

Mol"e*cule (?), n. [Dim. fr. L. moles a mass: cf. F. mol'ecule. See 3d Mole.]

1.

One of the very small invisible particles of which all matter is supposed to consist.

2. Physics

The smallest part of any substance which possesses the characteristic properties and qualities of that substance, and which can exist alone in a free state.

3. Chem.

A group of atoms so united and combined by chemical affinity that they form a complete, integrated whole, being the smallest portion of any particular compound that can exist in a free state; as, a molecule of water consists of two atoms of hydrogen and one of oxygen. Cf. Atom.

© Webster 1913.