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8873 / 2027
H1 Chemistry

Chemistry study notes

Atomic Structure

Use particles, orbitals and ionisation data to explain the behaviour of atoms and ions.

A-Level 8873, revised syllabus (2026-2027)

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3 topics

  1. Nucleus and charge

    Read particle counts and field evidence.

  2. Electrons in orbitals

    Build configurations from shell and subshell rules.

  3. Reading energy data

    Explain attraction and infer the arrangement.

Scope

Learning outcomes

1. Atomic Structure (8873, 2026 revision; examinations 2026 and 2027). Use the outcome map to find the explanation for a particular syllabus requirement.

See the learning outcome map

  1. 1(a) Identify the subatomic particles.

    • Relative charges and masses of protons, neutrons and electrons.

    Count particles before counting electrons

  2. 1(b) Predict beam deflection.

    • Proton, neutron and electron beams in an electric field; conditions for comparing deflection.

    Use a field to identify the charge

  3. 1(c) Locate atomic mass and charge.

    • Small positive nucleus; almost all mass in the nucleus; electrons outside.

    Count particles before counting electrons

  4. 1(d) Count particles in atoms and ions.

    • Given proton number, nucleon number and charge.

    Count particles before counting electrons

  5. 1(e) Interpret nuclear notation and isotopes.

    • (i) Protons/neutrons in Z and A.
    • (ii) Isotopes distinguished by neutron number.

    Count particles before counting electrons

  6. 1(f) Organise shells, subshells and orbitals.

    • Numbers and relative energies of s, p and d orbitals for n = 1, 2, 3, plus 4s and 4p.

    Replace circular paths with orbitals

  7. 1(g) Describe s and p shapes.

    • Spherical s and two-lobed p orbitals; no wave functions.

    Replace circular paths with orbitals

  8. 1(h) Write atom and ion configurations.

    • Use proton number and charge; filling, pairing, Cr/Cu exceptions and 4s removal.

    Build a configuration, then make the ion

  9. 1(i) Explain ionisation energies.

    • Nuclear charge, shielding, distance, subshell and pairing; Periodic Table/Data Booklet application.

    Explain how strongly an electron is held

  10. 1(j) Infer configurations from successive energies.

    • Identify shell jumps; recover the shell populations and full configuration when a complete data set is supplied; distinguish limited data.

    Find the jump that reveals the outer electrons

  11. 1(k) Connect successive energies to periodic position.

    • Use outer-electron count for main-group position and the number of occupied shells for period when supported by complete data.

    Find the jump that reveals the outer electrons