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H2 Chemistry

Chemistry study notes

The Periodic Table

Explain trends from electrons and structure, then predict the oxides, chlorides and redox behaviour of unfamiliar elements.

A-Level 9476 (2026-2027)

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6 topics

  1. Electronic structure and atomic trends

    Compare radius, ionisation energy and electronegativity across and down.

  2. Melting, conduction and volatility

    Use the actual particles and bonding in the elements.

  3. Period-3 oxides and hydroxides

    Track oxidation numbers, reactions with water and acid-base behaviour.

  4. Period-3 chlorides in water

    Distinguish dissolution, hydrated-ion hydrolysis and molecular hydrolysis.

  5. Group 2 and Group 17 chemistry

    Use electrode potentials and explain thermal stability.

  6. Predict and identify

    Combine independent physical and chemical clues.

Scope and references

Learning outcomes and sources

5. The Periodic Table. Use the outcome map to find the explanation for a particular syllabus requirement.

See the learning outcome map

  1. 5(a) Recognise electronic-configuration patterns.

    • Period 3 Na-Cl
    • Group 2 Mg-Ba
    • Group 17 Cl-I

    A period fills a shell; a group preserves an outer pattern

  2. 5(b) Explain atomic and ionic size, first IE and electronegativity trends.

    • (i) Across a period: shielding and nuclear charge
    • (ii) Down a group: shell number, shielding and nuclear charge
    • Subshell/pairing variations and isoelectronic ions

    Compare attraction, shielding and shell number together

  3. 5(c) Interpret melting and conductivity across the period.

    • Metallic elements
    • Giant molecular silicon
    • Simple molecular phosphorus, sulfur and chlorine

    Melting-point patterns reveal changes of structure

  4. 5(d) Explain halogen volatility.

    • Cl2, Br2, I2
    • Instantaneous dipole-induced dipole attraction
    • Polarizability, not X-X bond breaking

    Melting-point patterns reveal changes of structure

  5. 5(e) Explain the specified oxide and chloride patterns.

    • (i) Highest oxidation numbers: Na2O, MgO, Al2O3, SiO2, P4O10, SO3; NaCl, MgCl2, AlCl3, SiCl4, PCl5
    • (ii) Electronegativity and bonding, with AlCl3 treated separately
    • (iii) Water reactions of all six oxides
    • (iv) Acid/base behaviour of all six oxides and NaOH, Mg(OH)2, Al(OH)3; amphoteric reactions with acids and NaOH
    • (v) Water reactions of all five chlorides
    • (vi) Infer oxide/chloride structure from physical and chemical observations

    Highest oxides progress from ionic bases to covalent acidsAmphoteric aluminium compounds react on both sidesDissolving a chloride is not always the same as hydrolysing it

  6. 5(f) Use standard potentials to compare reactivity.

    • (i) Group 2 reducing agents
    • (ii) Group 17 oxidising agents
    • Written half-reaction direction and standard conditions

    Read reduction potentials in their written direction

  7. 5(g) Explain thermal-stability trends.

    • (i) Group 2 carbonates: cation charge density and anion polarizability
    • (ii) Group 17 hydrides: covalent bond energies

    Two thermal trends need two different explanations

  8. 5(h) Predict properties from group membership.

    • Transfer known periodic mechanisms to another member of a specified group

    Combine the clues before assigning an element

  9. 5(i) Infer periodic position and identity from evidence.

    • Physical and chemical properties
    • Nature and likely position
    • Check whether the evidence establishes a unique identity

    Combine the clues before assigning an element