A technique that ionizes atoms or molecules and separates them by mass-to-charge ratio to determine isotopic abundance and molecular mass.
Practise Atomic Structure & Periodicity All Atomic Structure & Periodicity topics
In mass spectrometry a sample is ionised, the ions are accelerated and then deflected by a magnetic or electric field, and the separated ions are detected. Ions with a smaller mass-to-charge ratio are deflected more strongly, so the spectrum separates the species by m/z. Peak heights are proportional to abundance, which gives isotopic composition directly. The technique also gives the molecular mass of compounds and the masses of their fragments, which helps identify unknown substances. It is used in drug testing, geochemistry and proteomics.
Key ideas: A sample is ionized, accelerated, deflected by a magnetic field and detected by mass to charge ratio m/z; lighter ions bend more. The radius is r = mv / (qB) and the peak height gives abundance. Peaks at m/z for isotopes give the weighted atomic mass, and the molecular ion peak M+ gives molar mass.
Common mistakes and connections: Students read the peak position as mass when charge is not 1, and forget that the tallest peak is not always the molecular ion. Fragments help determine structure. Cl2 gives patterns of 70, 72, 74 due to 35Cl and 37Cl combinations in a 9:6:1 ratio. It links to isotope abundances and relative atomic mass.
A mass spectrum of magnesium separates its three isotopes Mg-24, Mg-25 and Mg-26 by mass-to-charge ratio; peak heights give their abundances. The interactive lesson shows this as a live animation or chart.
Chlorine gas shows peaks at m/z 35 and 37 in an intensity ratio of about 3 to 1, reflecting its natural isotopes.
A technique that ionizes atoms or molecules and separates them by mass-to-charge ratio to determine isotopic abundance and molecular mass.
Mass Spectrometry is a intermediate topic in Atomic Structure & Periodicity. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Atomic Structure & Periodicity first: Mole, Avogadro's Number, Molar Mass.
The next topics in Atomic Structure & Periodicity are Cathode Rays and Millikan's Oil Drop Experiment.
Yes. The interactive lesson includes a self-check question on Mass Spectrometry, and the Atomic Structure & Periodicity quiz draws on every topic in this area.
Mass Spectrometry is topic 29 of 115 in Atomic Structure & Periodicity.