Introduction

Mass Spectrometry is a very important technique used by chemists in research laboratories. You should be able to understand the basic principles of this technique and interpret spectra obtained to deduce the chemical composition of a given sample.

Readin

Edexcel AS/A Level Chemistry Student Book 1 pages 12 to 15, pages 32 to 33

Tasks

Complete the following:

Read pages 12 to 15, making appropriate notes (include key definitions).
Complete the ‘in-text’ questions.

WATCH – Mass Spectrometer (RSC)

Complete questions 1 and 6 on pages 32 to 33.

Top Tips

Make sure that you understand the following key points:

The Z number is not the same as the relative isotopic mass. This is the number which appears on the periodic table which takes account of the relative proportion of each isotope of an element so Z might not be a whole number.
You should use the Z number in calculations.
When considering spectra of molecules always look for the molecular ion peak (M) which will be furthest to the right. In larger molecules there might be a tiny peak due to the presence of ¹³C, the M+1 peak. Ignore this.

Key Terms

Add the following subject vocabulary with definitions to your glossary.

Relative atomic mass A_r
Relative isotopic mass
Molecular ion peak