what is an angstrom

An angstrom or ångström is a metric unit of length used to measure very small distances. It is equal to 10⁻¹⁰ m, which is one ten-billionth of a meter, a hundred-millionth of a centimeter, 0.1 nanometer, or 100 picometers. The unit is named after the Swedish physicist Anders Jonas Ångström (1814–1874) . The angstrom is often used in the natural sciences and technology 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. For example, the atomic (covalent) radii of phosphorus, sulfur, and chlorine are about 1 angstrom, while that of hydrogen is about 0.5 angstroms. Visible light has wavelengths in the range of 4000–7000 Å. Although still widely used in physics and chemistry, the angstrom is not a formal part of the International System of Units (SI) . The closest SI unit is the nanometer (10−9 m) .