Periodicity & Inorganic is a core part of A-Level Chemistry. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Atomic radiusDecreases left to right across period.
Ionisation energyGenerally increases across period.
ElectronegativityIncreases left to right; F highest.
MP/BPPeak at Si (giant covalent); low at Ar.
ShieldingInner e- reduce nuclear attraction.
Effective ZNet nuclear charge felt by outer e-.
Na with H2OVigorous; NaOH + H2 produced.
Mg with H2OSlow with cold; vigorous with steam -> MgO.
Combustion in O2Most form oxides; vary in vigour.
Cl2 with metalsAnhydrous metal chlorides formed.
Si reactivityUnreactive with water at standard T.
P with O2Spontaneous; gives P4O10.
Basic oxideReacts with acid; ionic (Na2O, MgO).
AmphotericReacts as acid and base (Al2O3).
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
Why does atomic radius increase down a group?✗ Atoms get bigger down a group because they have more protons attracting more matter. ✓ Each successive element has an additional electron shell, increasing the distance of outer electrons from the nucleus.
Why does first ionisation energy generally increase across a period?✗ Atoms get bigger across a period, making electrons easier to add but harder to remove. ✓ Nuclear charge increases while shielding stays roughly constant, so electrons are held more tightly.
Why is the 4s orbital filled before the 3d orbital?✗ Because the 4s shell is closer to the nucleus than the 3d shell. ✓ Because the 4s orbital has a lower energy than 3d when both are empty, so electrons fill it first.
Why does Al have lower 1st IE than Mg?✗ Al has more shielding from core ✓ 3p electron easier to remove than 3s
Why do metals conduct electricity?✗ Metal atoms themselves move to carry the current. ✓ Delocalised electrons are free to move through the lattice of positive ions, carrying charge.
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