Ångström
The ångström (Swedish: [ˈɔŋstrøm]) or angstrom is a unit of length equal to 10 m (one ten-billionth of a metre) or 0.1 nm. Its symbol is Å, a letter in the Swedish alphabet.
The natural sciences and technology often use ångström to express sizes of atoms, molecules, microscopic biological structures, and lengths of chemical bonds, arrangement of atoms in crystals, wavelengths of electromagnetic radiation, and dimensions of integrated circuit parts. Atoms of phosphorus, sulfur, and chlorine are about an ångström in covalent radius, while a hydrogen atom is about half an ångström; see atomic radius.