Ångströms and Nanometres in Science
The ångström (Å) equals 10⁻¹⁰ metres, or 0.1 nanometres. It was historically the standard unit for atomic and molecular dimensions because the radii of atoms range from about 0.5 Å (hydrogen) to 2.5 Å (caesium), and chemical bond lengths fall between 1–3 Å. Today, nanometres (nm) have largely replaced ångströms in modern scientific literature, but ångströms remain common in crystallography and spectroscopy. The conversion is exactly 1 Å = 0.1 nm, or 10 Å = 1 nm.
Visible light wavelengths range from 380–700 nm (3,800–7,000 Å). X-rays used in crystallography have wavelengths of 0.5–2.5 Å, ideal for resolving atomic-scale structures. The spacing between atomic planes in a crystal (d-spacing) is typically expressed in ångströms in the Bragg equation: nλ = 2d sin θ.
Ångström to Nanometre Reference
| Ångströms (Å) | Nanometres (nm) | Example |
|---|---|---|
| 1 | 0.1 | H atom radius ≈ 0.53 Å |
| 10 | 1 | Typical protein segment |
| 100 | 10 | Small DNA fragment |
| 1000 | 100 | HIV virus diameter ≈ 100 nm |
| 3800 | 380 | Violet light (boundary UV) |
| 7000 | 700 | Red light (boundary IR) |
