Mass spectrometry

Background

1.14 - 1.17 Atomic structure

If a nucleus was the size of a raisin, the rest of the atom would be the size of a sports stadium

https://www.mychem.co.uk/index.php/igcse-chemistry/principles-of-chemistry/atomic-structure

how it works

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A mass spectrometer "sorts" particles according to their mass. A mass spectrum gives the relative abundance of particles of different masses. With an element - the relative abundance of the isotopes is given .This data is then used to calculate the relative atomic mass of the element.

Use the data here to calculate the Ar of lead.

When an organic molecule is analysed in a mass spectrometer the vaporisation and bombardment by high energy electrons process also fragments the molecule.

Ions are detected . Uncharged fragments will not be accelerated by the magnetic field and therefore get drawn out of the spectrometer by the vacuum pump.

This produces a fragmentation pattern which provides a "fingerprint" for the molecule but also other information which can help identify the molecule.

Study the two infra red spectra on the left. One is propan- 1- ol, the other is propan 2 ol. Which is which?

Infra red absorption data

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Intro image