// FIELD GUIDE 12 — LEVEL L3 (GCSE / NATIONAL 5)
Periodic trends
The table isn't just a list — it's arranged so properties change in predictable patterns as you move across or down it. Pick a trend and watch it play out across real elements.
// FIG. 01 — PICK A TREND
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// L3 — WHY TRENDS EXIST
Every trend comes back to the same two things: how many shells of electrons an atom has, and how strongly its nucleus pulls on the outer ones. Add a shell (moving down a group) and the outer electrons sit further away, feeling a weaker pull. Add protons without adding a shell (moving across a period) and the pull gets stronger.
Atomic radius
Shrinks across a period (stronger pull, same shell count), grows down a group (an extra shell each time).
Reactivity (metals)
Increases down Group 1/2 — outer electrons are further from the nucleus and easier to lose.
Melting point
Follows bonding strength — spikes in the middle of a period where metallic bonding is strongest.
// REFERENCES & FURTHER READING
Cross-check against your own exam board's specification (AQA, Edexcel, OCR, SQA).