CIE AS Chemistry (9701) exams from 2022

Revision Notes

1.1.5 Isotopes

Isotopes: Basics

  • Isotopes are atoms of the same element that contain the same number of protons and electrons but a different number of neutrons
  • The symbol for an isotope is the chemical symbol (or word) followed by a dash and then the mass number
    • Eg. carbon-12 and carbon-14 are isotopes of carbon containing 6 and 8 neutrons respectively

Atomic Structure Hydrogen Isotopes, downloadable AS & A Level Chemistry revision notes

The atomic structure and symbols of the three isotopes of hydrogen

Isotopes: Chemical & Physical Properties

  • Isotopes have similar chemical properties but different physical properties

Chemical properties

  • Isotopes of the same element display the same chemical characteristics
  • This is because they have the same number of electrons in their outer shells
  • Electrons take part in chemical reactions and therefore determine the chemistry of an atom

Physical properties

  • The only difference between isotopes is the number of neutrons
  • Since these are neutral subatomic particles, they only add mass to the atom
  • As a result of this, isotopes have different physical properties such as small differences in their mass and density

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Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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