Isotopes of an element have the same chemical properties but different physical properties. Explain why isotopes of the same element have the same chemical properties but may have different physical properties.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Isotopes have the same number of protons, giving them the same atomic number.
They also have the same number of electrons and the same electron configuration.
Because chemical properties are determined by the number and arrangement of electrons, isotopes react in the same way.
However, isotopes differ in the number of neutrons, giving them different mass numbers and masses, which influences physical properties such as density or melting point.
They also have the same number of electrons and the same electron configuration.
Because chemical properties are determined by the number and arrangement of electrons, isotopes react in the same way.
However, isotopes differ in the number of neutrons, giving them different mass numbers and masses, which influences physical properties such as density or melting point.
Examiner tips
- State that isotopes share the same atomic number and electron configuration to justify identical chemistry.
- Mention the role of neutrons in mass differences to explain varying physical properties.
- Use the word ‘isotopes’ and ‘neutrons’ to show understanding of terminology.
- Keep the answer concise and directly linked to the marks given.
Common mistakes
- Confusing isotopes with ions – forgetting that ions have different electron numbers.
- Saying isotopes have different chemical properties – they do not.
Mark scheme (4 marks)
- Isotopes have the same number of protons / same atomic number
- Isotopes have the same number of electrons (and the same electron arrangement / configuration)
- Chemical properties depend on the number / arrangement of electrons, so isotopes react in the same way
- Isotopes have different numbers of neutrons, giving them different mass numbers / different masses, which affects physical properties such as density or melting point
Key terms in this question
isotopes · chemical properties · physical properties
Related
- All Eduqas GCSE Chemistry revision notes →
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