Copper has two naturally occurring isotopes: copper-63 and copper-65. Explain what is meant by the term isotope and describe how the subatomic particles in copper-63 and copper-65 differ from each other.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Copper is a metal widely used in electrical wiring. Its atomic number is 29.
Model answer (4 marks)
Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.
Both copper‑63 and copper‑65 have 29 protons, because the atomic number of copper is 29.
Copper‑63 has a mass number of 63, so it contains 63 − 29 = 34 neutrons. Copper‑65 has a mass number of 65, so it contains 65 − 29 = 36 neutrons.
Because the number of protons is the same, both isotopes have the same number of electrons (29) and therefore the same electron configuration and chemical properties.
Both copper‑63 and copper‑65 have 29 protons, because the atomic number of copper is 29.
Copper‑63 has a mass number of 63, so it contains 63 − 29 = 34 neutrons. Copper‑65 has a mass number of 65, so it contains 65 − 29 = 36 neutrons.
Because the number of protons is the same, both isotopes have the same number of electrons (29) and therefore the same electron configuration and chemical properties.
Examiner tips
- Use the definition of isotope first, then give the proton count, neutron count and electron count for each isotope.
- Show the calculation for neutrons (mass number minus atomic number).
- Mention that chemical properties are unchanged because electron configuration is the same.
Common mistakes
- Confusing mass number with atomic number; writing 29 neutrons instead of 34 or 36.
- Omitting the calculation of neutrons or the statement that electrons are unchanged.
- Using the word ‘atoms’ instead of ‘isotopes’ in the definition.
Mark scheme (4 marks)
- Isotopes are atoms of the same element with the same number of protons but a different number of neutrons
- Both isotopes have 29 protons (as atomic number is 29)
- Copper-63 has 34 neutrons and copper-65 has 36 neutrons (mass number minus atomic number)
- Both isotopes have the same number of electrons (29), so the electron configuration / chemical properties are the same
Key terms in this question
Related
- All OCR GCSE Chemistry A: Gateway Science (J248) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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