Nitrogen has atomic number 7 and mass number 14. A different isotope of nitrogen has mass number 15. State the number of protons, neutrons and electrons in one atom of nitrogen-14, and explain how the structure of a nitrogen-15 atom differs from a nitrogen-14 atom.

Pearson Edexcel International GCSE Chemistry (4CH1) — 1.3 Atomic structure · State and Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Nitrogen‑14:
1. 7 protons
2. 7 neutrons
3. 7 electrons

Nitrogen‑15:
4. It has the same 7 protons and 7 electrons as nitrogen‑14, but one additional neutron (8 neutrons).

Examiner tips

  • Use the command word ‘state’ for the first part, then ‘explain’ for the difference.
  • Show the numbers clearly and link the extra neutron to the mass number increase.
  • Remember to keep the answer concise and to the point.

Common mistakes

  • Confusing the number of neutrons in nitrogen‑14 (should be 7, not 6).
  • Forgetting to mention that the number of protons and electrons remains unchanged in the isotope.

Mark scheme (4 marks)

  1. Nitrogen-14 has 7 protons
  2. Nitrogen-14 has 7 neutrons
  3. Nitrogen-14 has 7 electrons
  4. Nitrogen-15 has one more neutron (8 neutrons) than nitrogen-14 but the same number of protons (and electrons)

Key terms in this question

atomic number · mass number · isotope · neutron · proton · electron

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