Topic overview

Start with the big picture

The electromagnetic spectrum runs from gamma rays, with the highest energy and shortest wavelengths, through X-rays, ultraviolet, visible, infrared, microwaves, and radiofrequency. Because energy increases as wavelength decreases, different regions probe different molecular behavior. UV-Visible spectroscopy examines electronic transitions and can reveal effects of conjugation; IR spectroscopy measures bond vibrations and helps identify functional groups through characteristic absorptions. NMR uses radiofrequency radiation to observe nuclear spin transitions, with chemical shifts reflecting electronic shielding and coupling providing information about neighboring hydrogens. Mass spectrometry ionizes molecules and uses mass-to-charge signals, isotope patterns, and fragmentation to aid structural analysis. No single method supplies every kind of evidence, so combining techniques can support structure determination.