Nanometer: definition in chemistry
Nanometer: A unit of length equal to one billionth of a meter (10⁻⁹ m), with the symbol nm.
The nanometer is a convenient scale for atoms, molecules and the wavelengths of light. Most atoms are between about 0.1 and 0.5 nm across, and visible light has wavelengths of roughly 400 to 700 nm. Atomic sizes are also often given in picometers, where 1 nm equals 1,000 pm, and materials engineered at a scale of about 1 to 100 nm are called nanomaterials.
Examples
- A hydrogen atom is about 0.1 nm across
- The DNA double helix is about 2 nm wide
- Green light has a wavelength of about 530 nm
- A human hair is tens of thousands of nanometers thick
On the periodic table
Atomic radii are small fractions of a nanometer, from about 0.03 nm for hydrogen to roughly a quarter of a nanometer for cesium, so they are often given in picometers instead.