$word_{count}$: 250

Inert pair effect (very high frequency): Know which OS is more stable for Tl, Pb, Bi. PbO2 is an oxidiser ($Pb^{4+}$ to $Pb^{2+}$). SnCl2 is a reducer ($Sn^{2+}$ to $Sn^{4+}$). Practice comparison questions.

First element anomaly (every exam): Why NCl5 doesn't exist (no d-orbitals). Why SiCl4 hydrolyses but CCl4 doesn't. Why F-F is weak. Why HF is weak acid. These are direct-recall questions worth 4 marks.

Oxyacid basicity of P (very high frequency): Basicity = P-OH bonds. H3PO2=1, H3PO3=2, H3PO4=3. P-H bonds are non-ionisable but reducing. Quick formula: basicity = total H - P-H bonds.

Oxyacids of Cl (frequently tested paradox): Acid strength: HClO < HClO4. Oxidising power: HClO > HClO4. Inverse relationship. Know the reason for each trend.

Structures: Know shapes of XeF2 (linear), XeF4 (sq. planar), XeF6 (dist. oct.), ClF3 (T-shape), IF5 (sq. pyramid), IF7 (pentagonal bipyramid). Count electron pairs correctly.

Diagonal relationships: B-Si, Be-Al. Know 3-4 similarities for each pair.

Comparative trends: Acid strength of HX (HI>HBr>HCl>HF). Oxidising power of X2 (F2>Cl2>Br2>I2). Bond energy of X2 (Cl-Cl highest, not F-F). Boiling point of HX (HF highest, then HI>HBr>HCl).

Time management: Structure/shape questions take 30 seconds. Oxyacid basicity takes 15 seconds if you know the rule. Inert pair effect comparison takes 1 minute. Don't over-think.