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Secondary Chemistry Study notes

Bonding and Structure

Why salt, candle wax and copper behave differently: the particles, attractions and moving charges behind their properties.

O-Level 2026 SEC G3 2027

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5 topics

  1. Particles and substances

    Distinguish atoms, molecules and ions, then classify elements, compounds and mixtures.

  2. Ionic bonding and properties

    Follow electron transfer, build the idea of a lattice, and explain when ions can carry charge.

  3. Covalent bonding and molecules

    Read shared electron pairs and distinguish bonds within molecules from attractions between them.

  4. Metals and alloys

    Recognize metals and alloys and connect their properties to their arrangement.

  5. Work backwards from the evidence

    Use melting point and conductivity together to identify and explain a likely structure.

Scope and references

Your syllabus, covered

These notes cover Chemical Bonding and Structure (topic 3) for Combined Science Chemistry. Explanations, examples and diagrams are original, checked against the official learning outcomes below.

See how the learning outcomes map to these notes

  1. 3.1(a) Form ions by electron transfer

    • Electron loss produces a positive ion; electron gain produces a negative ion
    • Usual noble-gas electron arrangements and unchanged nuclei

    Ionic bonding: transfer, then attraction

  2. 3.1(b) Represent ionic bond formation

    • Metal and non-metal examples NaCl and MgCl2
    • Dot-and-cross electron accounting, ion charges and formula ratios

    Ionic bonding: transfer, then attraction

  3. 3.1(c) Explain ionic physical properties

    • Strong lattice attractions and high melting points
    • Fixed ions in a solid; mobile ions when molten or dissolved

    Why salt melts high but conducts only when ions moveWork backwards from the evidence

  4. 3.2(a) Explain a covalent bond

    • A shared electron pair
    • Usual full outer shells, including the two-electron first shell

    Covalent bonding: count shared pairs

  5. 3.2(b) Draw the named covalent molecules

    • Dot-and-cross diagrams for H2, O2, H2O, CH4 and CO2
    • Shared pairs and lone pairs

    Covalent bonding: count shared pairs

  6. 3.2(c) Deduce another molecule from its electrons

    • Count valence electrons, place bonds and check outer shells
    • Apply the method to an unfamiliar simple molecule

    Covalent bonding: count shared pairs

  7. 3.2(d) Connect covalent structure and properties

    • Distinguish covalent bonds from intermolecular attractions
    • Melting, boiling and electrical conductivity from the actual particles and structure

    Strong bonds inside; weaker attractions betweenWork backwards from the evidence

  8. 3.3(a) Distinguish an element, compound and mixture

    • Particle identity and chemical combination
    • A molecular element is still an element; a compound need not consist of molecules

    First, identify the particles

  9. 3.3(b) Describe the general properties of metals

    • Generally high melting and boiling points
    • Malleability and good conduction of heat and electricity

    Metals and alloys: properties from arrangement

  10. 3.3(c) Recognise an alloy

    • A mixture containing a metal and another element
    • Brass and stainless steel

    Metals and alloys: properties from arrangement

  11. 3.3(d) Identify metals and alloys in diagrams

    • A regular arrangement in a pure metal
    • Different particles in an alloy representation

    Metals and alloys: properties from arrangement