BRAINCAKEThe Molecular Ion Peak
The molecular ion peak, M+, is produced by molecules that have lost one electron but have not broken apart:
M(g) → M+(g) + e−
Because the molecular ion has the same mass as the whole molecule, it is the peak with the highest m/z value in the spectrum, ignoring the very small M+1 peak one unit above it. Its m/z value gives the relative molecular mass, Mr, of the compound.
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Key terms in this lesson
- mass-to-charge ratio
- The ratio of the mass of an ion to its charge, given the symbol m/z, used to identify ions in a mass spectrum.
More in Analytical Techniques
- Bond Vibrations and IR Absorption
- Characteristic IR Absorptions
- Interpreting IR Spectra
- IR in Breathalysers and Pollution Monitoring
- Mass Spectrometry of Organic Compounds
- The M+1 Peak
- Fragmentation
- Combining IR and Mass Spectra
All 10 lessons in Analytical Techniques · All OCR AS-level Chemistry topics