Lesson 2.1.1

2.1.1 Atomic structure and isotopes Quiz: OCR Chemistry, Unit 1

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 2.1.1, Atomic structure and isotopes: 20 multiple choice questions for the OCR Chemistry (H432), Unit 1: Foundations in chemistry, written with Revision Ninja.

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The 20 questions

  1. Which subatomic particles differ in number between isotopes of the same element?

    • Positrons
    • Neutrons
    • Electrons
    • Protons

  2. An atom has atomic number 17 and mass number 35. How many neutrons does this atom contain?

    • 18
    • 52
    • 35
    • 17

  3. How many electrons are in a Mg2+ ion? (Mg has atomic number 12)

    • 10
    • 14
    • 24
    • 12

  4. An ion has 16 protons, 16 neutrons and 18 electrons. Which ion is it?

    • S2+ (sulfur cation)
    • S2- (sulfide ion)
    • Ar (argon atom)
    • Cl- (chloride ion)

  5. Relative isotopic mass is measured compared to one-twelfth the mass of which atom?

    • Hydrogen-1
    • Carbon-12
    • Carbon-13
    • Carbon-14

  6. Boron has two isotopes, 10B (19.9%) and 11B (80.1%). What is the relative atomic mass of boron to 2 decimal places?

    • 10.00
    • 10.20
    • 10.80
    • 11.00

  7. A mass spectrum of magnesium shows peaks at m/z 24, 25 and 26 with relative abundances 79%, 10% and 11%. What is the relative atomic mass?

    • 24.00
    • 25.00
    • 24.32
    • 24.80

  8. What is the relative formula mass of calcium hydroxide, Ca(OH)2? (Ar: Ca 40.1, O 16.0, H 1.0)

    • 57.1
    • 74.1
    • 40.1
    • 91.1

  9. What is the relative molecular mass of ethanoic acid, C2H4O2? (Ar: C 12.0, H 1.0, O 16.0)

    • 44.0
    • 58.0
    • 62.0
    • 60.0

  10. Chlorine has isotopes 35Cl and 37Cl in a 75:25 ratio. What is the relative atomic mass of chlorine?

    • 36.0
    • 35.0
    • 37.0
    • 35.5

  11. An ion has mass number 56, 26 protons and 24 electrons. What is its charge?

    • 24+
    • 2-
    • 2+
    • 0

  12. A nuclide has mass number 81 and 46 neutrons. What is its atomic number?

    • 116
    • 46
    • 81
    • 35

  13. Why is the relative atomic mass of chlorine not a whole number?

    • Weighted mean mass
    • Loss of electrons
    • Presence of impurities
    • Unstable nucleus

  14. Element Y has isotopes 69Y and 71Y and a relative atomic mass of 69.7. What is the approximate percentage abundance of 69Y?

    • 35%
    • 65%
    • 70%
    • 50%

  15. Copper has isotopes 63Cu and 65Cu with relative atomic mass 63.5. What is the approximate percentage of 65Cu?

    • 50%
    • 25%
    • 63%
    • 75%

  16. An ion has mass number 27, 10 electrons and charge 3+. How many neutrons does it contain?

    • 10
    • 14
    • 17
    • 13

  17. Carbon has relative atomic mass 12.011, with isotopes 12C (mass 12.000) and 13C (mass 13.003). What is the approximate percentage of 13C?

    • about 1.5%
    • about 0.5%
    • about 11%
    • about 1.1%

  18. Which pair of nuclides are isotopes of each other?

    • 16O and 17O
    • 39K and 40Ca
    • 40Ar and 40Ca
    • 14C and 14N

  19. In a mass spectrum of an element, what does peak height represent?

    • Atomic radius
    • Isotopic mass
    • Relative abundance
    • Ionisation energy

  20. Which term describes the mass of giant ionic compounds like sodium chloride?

    • Relative isotopic mass
    • Relative molecular mass
    • Relative formula mass
    • Relative atomic mass

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