SEC G3 Combined Science Chemistry component K326/K328
C8: Patterns in the Periodic Table
Use Groups 1, 17, and 18, the reactivity series, extraction, alloys, and rust prevention within Combined scope.
Reviewed for the 2027 cohort on 19 July 2026. The official syllabus remains authoritative for assessable wording and paper details.
Core notes
Periodic patterns use proton number and outer-electron arrangement to predict properties, while reactivity evidence guides metal extraction and corrosion control.
Periodic organisation and prediction
The Periodic Table orders elements by increasing proton number. Period position relates to occupied shells and group position to outer electrons, so same-group elements show similar chemistry.
Across a period, character generally changes from metallic to non-metallic as outer-electron number increases. Use position and known group patterns to predict Group 1 and Group 17 properties.
Groups 1, 17, and 18
Lithium, sodium, and potassium are relatively soft, low-density metals. Down Group 1, melting point trends downward and reaction with water becomes more vigorous.
Group 17 elements are diatomic non-metals. Chlorine is a pale green gas, bromine a red-brown liquid, and iodine a grey-black solid at room conditions, so colour deepens and state changes down the group. Reactivity decreases down Group 17, and a more reactive halogen displaces a less reactive halide. Group 18 elements are unreactive because their outer electron shells are complete.
Metal reactivity, extraction, and rusting
Order K, Na, Ca, Mg, Zn, Fe, Pb, H, Cu, Ag using evidence from reactions with water, steam, and dilute hydrochloric acid. Deduce an unfamiliar order from observations rather than memorising a result that conflicts with the data.
More reactive metals are harder to obtain from ores. Iron rusts only when oxygen and water are present; paint, grease, or plastic coating prevents rust by forming a barrier.
Formulae and relationships
This chapter is assessed mainly through models, field patterns and explanations. Build the causal chain before adding any calculation.
Worked examples
Example 1: Metal X reacts with steam but not cold water and displaces copper from copper(II) sulfate. What can be deduced?
- Reaction with steam shows appreciable reactivity.
- Displacement shows X is above copper.
- The evidence does not by itself locate X exactly among every other metal.
Answer: X is more reactive than copper and reacts with steam, but more evidence is needed for an exact full-series position.
Chapter checkpoint
Use these three moves to organise the topic before attempting a mixed or practical question.
- Explain Periodic organisation and prediction with the named terms, evidence, and causal links kept distinct.
- Use Groups 1, 17, and 18 to interpret the evidence given and justify each conclusion.
- Apply Metal reactivity, extraction, and rusting to a new example, then check the conclusion against the information given.
Official outcome coverage
K326 C8: 13 mapped outcomes, references C8.1(a), C8.1(b), C8.1(c), C8.1(d), C8.1(e), C8.1(f), C8.2(a), C8.2(b), C8.2(c), C8.3(a), C8.3(b), C8.3(c), C8.3(d). Check the official K326 syllabus.
K328 C8: 13 mapped outcomes, references C8.1(a), C8.1(b), C8.1(c), C8.1(d), C8.1(e), C8.1(f), C8.2(a), C8.2(b), C8.2(c), C8.3(a), C8.3(b), C8.3(c), C8.3(d). Check the official K328 syllabus.
The outcome wording is not reproduced here. The relevant official syllabus remains authoritative for exact assessable scope.
Practical and data connection
Compare reactivity observations using equal metal quantities and equal water, steam or dilute-acid conditions. Separate measured evidence from the inferred order, and treat barrier protection from rusting as effective only while the coating remains intact.
Exam traps and retrieval check
Avoid these traps
- Ordering elements by atomic mass instead of proton number.
- Saying Group 18 is inert because it has no electrons.
- Claiming rusting needs oxygen but not water.
Check from memory
What number orders the Periodic Table?
Proton number.
Which group contains the halogens?
Group 17.
What two conditions are essential for rusting?
Oxygen and water.
Official Combined Science scope
This shared Combined Chemistry owner serves both K326 and K328. Periodic organisation, Groups 1, 17 and 18, the stated reactivity series, metal extraction, and barrier protection from rusting.