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Combined Science Chemistry

Chemistry study notes

Particles and Atoms

From changes of state to counting the particles in atoms and ions.

O-Level 5086 / 5088 (2026) / SEC G3 K326 / K328 (2027)

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3 topics

  1. States and changes of state

    Explain what particles do and where energy goes.

  2. Inside an atom

    Use charges, masses and shells to account for an atom.

  3. Atomic numbers, isotopes and ions

    Keep the identity of the element separate from its mass and charge.

Scope and references

Learning outcomes and sources

2. The Particulate Nature of Matter (5086 / 5088 / K326 / K328). Use the outcome map to find the explanation for a particular syllabus requirement.

See the learning outcome map

  1. 2.1(a) Explain states and their interconversion

    • Solid, liquid and gas particle arrangements and movements
    • Melting, freezing, boiling/evaporation, condensation, sublimation
    • Energy changes during state changes

    States and changes of state

  2. 2.2(a) Compare subatomic particles

    • Relative charges and approximate relative masses of proton, neutron, electron

    Inside an atom

  3. 2.2(b) Represent atomic structure

    • Nucleons in nucleus
    • Electrons in shells shown in a diagram
    • No s/p/d/f classification

    Inside an atom

  4. 2.2(c) Define proton and nucleon numbers

    • Proton number Z
    • Nucleon number A

    Atomic numbers, isotopes and ions

  5. 2.2(d) Read and write nuclide notation

    • Carbon-12 notation
    • Atomic and mass-number positions

    Atomic numbers, isotopes and ions

  6. 2.2(e) Recognize isotopes

    • Same proton number; different neutron number

    Atomic numbers, isotopes and ions

  7. 2.2(f) Count particles in atoms and ions

    • Use proton/nucleon numbers
    • Account for positive and negative ion charges

    Atomic numbers, isotopes and ions