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ASChemistryCIERevision Notes4. Analysis4.1 Analytical Techniques4.1.3 Isotopic Abundance & Relative Atomic Mass

Isotopic Abundance & Relative Atomic Mass (CIE AS Chemistry)

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Calculating Relative Atomic Mass

  • Isotopes are different atoms of the same element that contain the same number of protons and electrons but a different number of neutrons.
    • These are atoms of the same elements but with different mass numbers

  • Because of this, the mass of an element is given as relative atomic mass (Ar) by using the average mass of the isotopes
  • The relative atomic mass of an element can be calculated by using the relative abundance values
    • The relative abundance of an isotope is either given or can be read off the mass spectrum

Calculating Relative Atomic Mass equation 1

Worked example: Calculating relative atomic mass of oxygen

Analytical Techniques Worked example - Calculating relative atomic mass of oxygen, downloadable AS & A Level Chemistry revision notes

Answer 

The correct answer is 1

Calculating Relative Atomic Mass worked example equation 1

= 16.0044

= 16.00

Worked example: Calculating relative atomic mass of boron

Analytical Techniques Worked example - Calculating relative atomic mass of boron, downloadable AS & A Level Chemistry revision notes

Analytical Techniques Mass Spectrum Boron, downloadable AS & A Level Chemistry revision notes

Answer

Calculating Relative Atomic Mass worked example equation 2

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    Previous:4.1.2 Mass SpectrometryNext:4.1.4 Molecular Ion Peak & Fragmentation
    Francesca

    Author: Francesca

    Expertise: Head of Science

    Fran studied for a BSc in Chemistry with Forensic Science, and since graduating taught A level Chemistry in the UK for over 11 years. She studied for an MBA in Senior Leadership, and has held a number of roles during her time in Education, including Head of Chemistry, Head of Science and most recently as an Assistant Headteacher. In this role, she used her passion for education to drive improvement and success for staff and students across a number of subjects in addition to Science, supporting them to achieve their full potential. Fran has co-written Science textbooks, delivered CPD for teachers, and worked as an examiner for a number of UK exam boards.