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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Ultraviolet (UV)

Light with wavelengths from about 10 to 400 nm, just shorter than violet. UV photons are energetic enough to excite valence electrons and break many chemical bonds.

The electromagnetic spectrumFrom left to right: gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, radio waves. Wavelength increases to the right; frequency and photon energy increase to the left. Visible light spans about 400 nm (violet) to 700 nm (red).γ-rayX-rayUVIRmicrowaveradio400 nmvisible700 nmlonger wavelength →← higher frequency and photon energy

Example

Every hydrogen line ending on n=1n = 1 (the Lyman series, 91.2 to 122 nm) is in the UV. A 300 nm photon carries 399 kJ/mol, more than the 242 kJ/mol Cl–Cl bond energy.

See alsoElectromagnetic spectrumVisible lightLyman series