Chapter 2: Atoms, ions and compounds

Electron relative mass

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Isotope

atoms of an element that have different numbers of neutrons, different masses, and the same numbers of protons and electrons.

How may physical properties of isotopes slightly differ?

higher mass isotopes may have slightly higher melting/boiling points and density

Relative isotopic mass

the mass of an atom of an isotope compared to 1/12th of the mass of a carbon-12 atom

relative atomic mass

the weighted mean mass of an atom of an element compared to 1/12th of a carbon-12 atom

What is mass spectrometry used for?

find the abundance and mass of each isotope in an element (allows us to determine relative atomic mass)

Find the relative molecular mass of substances made of molecules

How does mass spectrometry work?

sample placed in mass spectrometer

Sample vaporised & ionised to form + ions

Ions accelerated (heavier ions slower and harder to deflect, so ions of each isotope are separated)

Ions detected on mass spectrum as mass to charge ratio (m/z) (the greater the abundance, the larger the signal)