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Atomic structure and isotopes: OCR A‑Level Chemistry A questions

Every OCR A-Level Chemistry A exam question on 2.1.1 Atomic structure and isotopes, 2016–2025, with its mark scheme and examiner’s report.

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1,820 questions

  1. Q1

    June 2025 · Paper 1

    1 mark2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2025 Paper 1, question 1: The table shows the number of protons and neutrons in four different atoms. Atom Number of protons Number of neutrons W 17 18 X 18 18 Y 19 18 Z 18 19 Which two

  2. Q1(a)(i)

    June 2025 · Paper 3

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2025 Paper 3, question 1(a)(i): Complete the table to show the number of protons, neutrons and electrons in the particles that cause the peaks at m/z 79 and 81. Number of Number of Number of m

  3. Q1(a)(ii)

    June 2025 · Paper 3

    3 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2025 Paper 3, question 1(a)(ii): Explain why there are peaks with m/z values of 158, 160 and 162 and predict their relative abundances. Explanation Relative abundances [3]

  4. Q21(a)

    June 2025 · AS Paper 1

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2025 AS Paper 1, question 21(a): This part of the question is about sulfur. Complete the table below. Species Protons Neutrons Electrons 34S 16 16 18 [2]

  5. Q21(b)

    June 2025 · AS Paper 1

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2025 AS Paper 1, question 21(b): The mass spectrum of a sample of magnesium is shown below. 75.45% Relative abundance 15.21% 9.34% 24 25 26 m / z Calculate the relative atomic mass of magnesium

  6. Q2

    June 2024 · AS Paper 1

    1 mark2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2024 AS Paper 1, question 2: Which row shows the atomic structure of 25Mg2+? 2 Protons Neutrons Electrons A 10 12 13 B 10 15 12 C 12 13 10 D 12 13 14 Your answer [1]

  7. Q21(a)

    June 2024 · AS Paper 1

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2024 AS Paper 1, question 21(a): A sample of iron is isolated from a meteorite and analysed by mass spectrometry. The mass spectrum shows peaks with the relative abundances below. 54Fe 56Fe 57F

  8. Q1(a)(i)

    June 2023 · AS Paper 2

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2023 AS Paper 2, question 1(a)(i): Calculate the relative atomic mass of titanium in the sample. Give your answer to 2 decimal places. relative atomic mass = [2]

  9. Q1(a)(iii)

    June 2023 · AS Paper 2

    1 mark2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2023 AS Paper 2, question 1(a)(iii): Complete the table to show the number of protons, neutrons and electrons in a 48Ti2+ ion. Protons Neutrons Electrons 48Ti2+ ion [1]

  10. Q1(b)(i)

    June 2022 · Paper 3

    1 mark2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2022 Paper 3, question 1(b)(i): What are the percentage compositions of copper and zinc in the brass sample? Cu = % Zn = % [1]

  11. Q1(b)(ii)

    June 2022 · Paper 3

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2022 Paper 3, question 1(b)(ii): Calculate the relative atomic mass of zinc in the sample of brass. Give your answer to 2 decimal places. relative atomic mass = [2]

  12. Q22(a)

    June 2022 · AS Paper 1

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2022 AS Paper 1, question 22(a): The relative atomic mass of a sample of osmium can be determined from its mass spectrum, shown below. 43.89% 27.23% relative abundance 16.75% (%) 12.13% 185 186

  13. Q22(b)

    June 2022 · AS Paper 1

    2 marks2.1.1 Atomic structure and isotopes2.2.1 Electron structure
    The whole paper ↗
    June 2022 AS Paper 1, question 22(b): Complete the table for an atom and an ion of two different elements. Mass Element Protons Neutrons Electron configuration Charge number 28 34 0 1s22s22p63s23p6

  14. Q21(b)

    November 2021 · AS Paper 1

    1 mark2.1.1 Atomic structure and isotopes
    The whole paper ↗
    November 2021 AS Paper 1, question 21(b): Selenium, Se, has the atomic number 34. 76Se and 82Se are two isotopes of selenium. Complete the table to show the numbers of protons, neutrons and electrons in

  15. Q21(c)

    November 2021 · AS Paper 1

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    November 2021 AS Paper 1, question 21(c): The relative atomic mass of an element can be determined from its mass spectrum. The table shows the results of a mass spectrum of a sample of sulfur, S. Isotop

  16. Q16(a)

    November 2020 · Paper 1

    1 mark2.1.1 Atomic structure and isotopes
    The whole paper ↗
    November 2020 Paper 1, question 16(a): Relative atomic mass is defined as ‘the weighted mean mass compared with 1/12th mass of carbon-12’. Explain what is meant by the term weighted mean mass. [1]

  17. Q21(b)

    November 2020 · AS Paper 1

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    November 2020 AS Paper 1, question 21(b): Most elements contain atoms of different isotopes. State any differences and similarities between the atomic structures of isotopes of the same element. Differe

  18. Q21(c)(i)

    November 2020 · AS Paper 1

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    November 2020 AS Paper 1, question 21(c)(i): Calculate the relative atomic mass of chlorine. Give your answer to 2 decimal places. relative atomic mass = [2]

  19. Q21(c)(ii)

    November 2020 · AS Paper 1

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    November 2020 AS Paper 1, question 21(c)(ii): The mass spectrum of chlorine, Cl 2, also contains three molecular ion, M+, peaks. One of the M+ peaks has an m /z value of 72. Suggest why an M+ peak at m /z =

  20. Q16(b)

    June 2019 · Paper 1

    2 marks2.1.1 Atomic structure and isotopes
    The whole paper ↗
    June 2019 Paper 1, question 16(b): A sample of magnesium, Ar = 24.305, is found to consist of three isotopes. The accurate relative isotopic masses and % abundances of two of the isotopes are sho
All 35 questions on Atomic structure and isotopes, as a list
  1. June 2025, Paper 1, Q1 (1 mark): The table shows the number of protons and neutrons in four different atoms. Atom Number of protons Number of neutrons W 17 18 X 18 18 Y 19 18 Z 18 19 Which two
  2. June 2025, Paper 3, Q1(a)(i) (2 marks): Complete the table to show the number of protons, neutrons and electrons in the particles that cause the peaks at m/z 79 and 81. Number of Number of Number of m
  3. June 2025, Paper 3, Q1(a)(ii) (3 marks): Explain why there are peaks with m/z values of 158, 160 and 162 and predict their relative abundances. Explanation Relative abundances [3]
  4. June 2025, AS Paper 1, Q21(a) (2 marks): This part of the question is about sulfur. Complete the table below. Species Protons Neutrons Electrons 34S 16 16 18 [2]
  5. June 2025, AS Paper 1, Q21(b) (2 marks): The mass spectrum of a sample of magnesium is shown below. 75.45% Relative abundance 15.21% 9.34% 24 25 26 m / z Calculate the relative atomic mass of magnesium
  6. June 2024, AS Paper 1, Q2 (1 mark): Which row shows the atomic structure of 25Mg2+? 2 Protons Neutrons Electrons A 10 12 13 B 10 15 12 C 12 13 10 D 12 13 14 Your answer [1]
  7. June 2024, AS Paper 1, Q21(a) (2 marks): A sample of iron is isolated from a meteorite and analysed by mass spectrometry. The mass spectrum shows peaks with the relative abundances below. 54Fe 56Fe 57F
  8. June 2023, AS Paper 2, Q1(a)(i) (2 marks): Calculate the relative atomic mass of titanium in the sample. Give your answer to 2 decimal places. relative atomic mass = [2]
  9. June 2023, AS Paper 2, Q1(a)(iii) (1 mark): Complete the table to show the number of protons, neutrons and electrons in a 48Ti2+ ion. Protons Neutrons Electrons 48Ti2+ ion [1]
  10. June 2022, Paper 3, Q1(b)(i) (1 mark): What are the percentage compositions of copper and zinc in the brass sample? Cu = % Zn = % [1]
  11. June 2022, Paper 3, Q1(b)(ii) (2 marks): Calculate the relative atomic mass of zinc in the sample of brass. Give your answer to 2 decimal places. relative atomic mass = [2]
  12. June 2022, AS Paper 1, Q22(a) (2 marks): The relative atomic mass of a sample of osmium can be determined from its mass spectrum, shown below. 43.89% 27.23% relative abundance 16.75% (%) 12.13% 185 186
  13. June 2022, AS Paper 1, Q22(b) (2 marks): Complete the table for an atom and an ion of two different elements. Mass Element Protons Neutrons Electron configuration Charge number 28 34 0 1s22s22p63s23p6
  14. November 2021, AS Paper 1, Q21(b) (1 mark): Selenium, Se, has the atomic number 34. 76Se and 82Se are two isotopes of selenium. Complete the table to show the numbers of protons, neutrons and electrons in
  15. November 2021, AS Paper 1, Q21(c) (2 marks): The relative atomic mass of an element can be determined from its mass spectrum. The table shows the results of a mass spectrum of a sample of sulfur, S. Isotop
  16. November 2020, Paper 1, Q16(a) (1 mark): Relative atomic mass is defined as ‘the weighted mean mass compared with 1/12th mass of carbon-12’. Explain what is meant by the term weighted mean mass. [1]
  17. November 2020, AS Paper 1, Q21(b) (2 marks): Most elements contain atoms of different isotopes. State any differences and similarities between the atomic structures of isotopes of the same element. Differe
  18. November 2020, AS Paper 1, Q21(c)(i) (2 marks): Calculate the relative atomic mass of chlorine. Give your answer to 2 decimal places. relative atomic mass = [2]
  19. November 2020, AS Paper 1, Q21(c)(ii) (2 marks): The mass spectrum of chlorine, Cl 2, also contains three molecular ion, M+, peaks. One of the M+ peaks has an m /z value of 72. Suggest why an M+ peak at m /z =
  20. June 2019, Paper 1, Q16(b) (2 marks): A sample of magnesium, Ar = 24.305, is found to consist of three isotopes. The accurate relative isotopic masses and % abundances of two of the isotopes are sho
  21. June 2019, Paper 3, Q1(b) (1 mark): Explain why a small proportion of molecules in water have a relative molecular mass of 20. [1]
  22. June 2019, AS Paper 1, Q21(a) (1 mark): Most elements contain different isotopes. State two differences between isotopes of the same element. [1]
  23. June 2019, AS Paper 1, Q21(b) (2 marks): Complete the table for an atom and an ion of two different elements. Mass Element Protons Neutrons Electrons Charge number 26 28 0 80 36 2− [2]
  24. June 2019, AS Paper 2, Q1(a)(i) (2 marks): Explain what is meant by the term relative atomic mass of an element. [2]
  25. June 2019, AS Paper 2, Q1(a)(ii) (2 marks): A sample of strontium has a relative atomic mass of 87.73. The sample consists of: • 82.9% Sr-88 • 6.9% Sr-87 • one other isotope. Determine the other isotope o
  26. June 2018, Paper 1, Q1 (1 mark): A sample of boron contains the isotopes 10B and 11B. 1 The relative atomic mass of the boron sample is 10.8. What is the percentage of 11B atoms in the sample o
  27. June 2018, AS Paper 1, Q21(a)(i) (1 mark): Complete the table to show the atomic structure of 30Si. Protons Neutrons Electrons 30Si [1]
  28. June 2018, AS Paper 1, Q21(a)(ii) (2 marks): A sample of silicon is analysed by mass spectrometry. The mass spectrum shows peaks with the relative abundances below. 28Si • 92.23% 29Si • 4.68% 30Si • 3.09%
  29. June 2017, Paper 1, Q1 (1 mark): Which atom is not an isotope of iodine? Number of neutrons Mass number A 72 125 B 74 127 C 75 128 D 77 129 Your answer [1]
  30. June 2017, AS Paper 1, Q1 (1 mark): Which ion has a different number of electrons from the other three ions? Ga3+ A Cl − B S2− C Ca2+ D Your answer [1]
  31. June 2017, AS Paper 1, Q22(a)(i) (2 marks): The species causing the peaks in the mass spectrum are 1+ ions of magnesium. Complete the table to show the number of protons, neutrons and electrons in each 1+
  32. June 2017, AS Paper 1, Q22(a)(ii) (2 marks): Calculate the relative atomic mass of the magnesium in the sample. Give your answer to two decimal places. relative atomic mass = [2]
  33. June 2016, AS Paper 1, Q1 (1 mark): Which row shows the atomic structure of 37Cl–? 1 protons neutrons electrons A 17 18 20 B 17 20 18 C 18 19 17 D 20 17 21 Your answer [1]
  34. June 2016, AS Paper 1, Q21(a) (2 marks): Copper and nickel each exist as a mixture of isotopes. State the similarities and differences between the atomic structure of isotopes of the same element. Simi
  35. June 2016, AS Paper 1, Q21(b)(i) (2 marks): Calculate the relative atomic mass of the copper used to make the coins. Give your answer to two decimal places. relative atomic mass = [2]

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