Mass Spectrometry
Use this landing page to move quickly between the key mass spectrometry revision pages for this section. Each card links to a focused page covering the instrument, RAM calculations and isotopic peak patterns.
Choose a Mass Spectrometry Page
Mass spectrometry separates positive ions according to their mass-to-charge ratio, written as m/z. These pages build from the operation of the mass spectrometer through to isotope abundance, relative atomic mass and interpreting molecular spectra.
Key idea: A mass spectrum is evidence. The positions of the peaks show m/z values, while the peak heights show relative abundance.
Spectrometer
The Mass Spectrometer
Revise vaporisation, ionisation, acceleration, deflection, detection and why ions are separated by m/z.
Calculations
RAM Calculations
Use isotopic mass and percentage abundance data to calculate relative atomic mass using weighted means.
Spectra
Predicting Diatomic Mass Spectra
Predict molecular ion peak patterns for diatomic molecules using isotope combinations and probability ratios.
Compounds
Identifying Compounds from Mass Spectra
Use the molecular ion peak, the M+1 peak and simple fragment peaks to find the relative molecular mass and identify an unknown compound.
How to Use These Pages
Start with the instrument so that you understand how ions are made and detected. Then move to RAM calculations, because isotope abundance links directly to peak heights. Finally, use the diatomic mass spectra page to practise interpreting isotope combinations and peak ratios as chemical evidence.
Exam focus: When explaining a spectrum, distinguish clearly between peak position and peak height. Peak position is linked to m/z. Peak height or relative intensity is linked to relative abundance.
Copyright notice: This revision page, including its written explanations, layout and teaching sequence, is produced for Online Learning System by Dr. Mohammed Al-Fatah. It is intended for student revision and may not be copied, redistributed or republished without permission.
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