Iron has atomic number 26. An atom of the most common isotope of iron has a mass number of 56. State the number of protons, neutrons and electrons in one atom of this isotope of iron. Then state what is meant by the term isotope.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Protons: 26
Neutrons: 30
Electrons: 26
Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.
Neutrons: 30
Electrons: 26
Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.
Examiner tips
- Use the exact numbers for protons, neutrons and electrons. Give the definition of isotope in one sentence. Keep the answer concise and in bullet or numbered form if allowed.
Common mistakes
- Confusing mass number with atomic number. Giving the wrong number of neutrons (e.g. 28 instead of 30). Omitting the definition of isotope or stating it incorrectly.
Mark scheme (4 marks)
- Number of protons = 26
- Number of neutrons = 30
- Number of electrons = 26
- Isotopes are atoms of the same element with the same number of protons but a different number of neutrons
Key terms in this question
atomic number · mass number · isotope · proton · neutron · electron
Related
- All Pearson Edexcel International GCSE Chemistry (4CH1) revision notes →
- How to answer a "State" question →
- Decode the mark scheme abbreviations →
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