Mass spectrometry
I can explain how mass spectrometry is used to identify isotopes and molecular structures, and calculate relative atomic masses.
Mass spectrometry
I can explain how mass spectrometry is used to identify isotopes and molecular structures, and calculate relative atomic masses.
Lesson details
Key learning points
- Isotopes are atoms of the same element with different numbers of neutrons.
- Relative abundances of isotopes can be used to calculate the relative atomic mass (RAM) of an element.
- Mass spectrometry ionises samples to create positive ions for analysis.
- The M⁺ peak represents the molecular ion, indicating the molecular mass.
- Fragmentation in mass spectrometry helps identify molecular structure by breaking molecules into smaller ions.
Common misconception
All peaks in a mass spectrum represent intact (and neutral) molecules or atoms.
Clarify that in mass spectrometry, all detected peaks represent ionised species, not neutral molecules or atoms. The peaks can correspond to either the molecular ion (M⁺) or smaller ionised fragments, as well as different isotopes of an element.
Keywords
Isotope - An atom of an element with the same number of protons, but different number of neutrons.
Relative atomic mass - An average value that takes account of the abundance of the isotopes of the element.
Molecular mass - The sum of the atomic masses of all the atoms in a molecule.
Molecular ion - The ion produced when the molecule is ionised by loss of an electron from the molecule.
Spectrometer - An apparatus used for recording and measuring spectra, especially as a method of analysis.
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
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