Molecule

A molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. The science of molecules is called molecular chemistry or molecular physics, depending on the particular aspect of focus. Molecular chemistry is concerned with the laws governing the interaction between molecules that results in the formation and breakage of chemical bonds, while molecular physics is concerned with the laws governing their structure and properties. In practice, however, this distinction is rather vague.

Size

Most molecules are much too small to be seen with the naked eye, but there are exceptions. DNA, a macromolecule, can reach macroscopic sizes.

Related Topics:
DNA - Macromolecule - Macroscopic

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The smallest molecule is the hydrogen molecule. The interatomic distance is 1.5 Å. But the size of its electron cloud is difficult to define precisely. Under normal conditions molecules have a dimension of a few to a few dozen Å.

Related Topics:
Hydrogen - Å - Electron cloud - Normal condition

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