Copper has two isotopes: copper-63 and copper-65. The relative atomic mass of copper is 63.5. Explain what the terms 'isotope' and 'relative atomic mass' mean, and use this information to describe what can be deduced about the abundance of the two isotopes of copper.

AQA GCSE Chemistry (8462) — 4.1.1 A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.

Relative atomic mass is an average value that takes account of the abundance of the isotopes of the element.

The relative atomic mass of copper is 63.5, which is closer to 63 than to 65.

Therefore copper‑63 is more abundant than copper‑65.

Examiner tips

  • Define isotopes and relative atomic mass clearly. Show the reasoning that 63.5 is nearer to 63. State the conclusion about abundance.
  • Use correct UK spelling and terminology.

Mark scheme (4 marks)

  1. Isotopes are atoms of the same element with the same number of protons but a different number of neutrons
  2. Relative atomic mass is an average value that takes account of the abundance of the isotopes of the element
  3. The relative atomic mass of 63.5 is closer to 63 than to 65
  4. Therefore copper-63 is more abundant than copper-65

Key terms in this question

isotope · relative atomic mass · abundance

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