Lewis structures, the whole VSEPR table, hybridisation, dipole moment and the weak forces — the chapter that decides every shape, angle and polarity question in the paper.
Unit 1 carries 17 of the 50 chemistry marks; with fourteen chapters sharing them, this one averages a little over one (MEC publishes weights by unit, not by chapter). Bonding pays twice over, because shape, hybridisation and polarity come back in the intermolecular forces of states of matter and in every reaction in general organic chemistry.
The MEC scope line runs: Electronic theory of valency. Ionic, covalent and co-ordinate covalent bonds. Lewis dot structures of s- and p-block compounds. VSEPR theory and the shape of simple molecules. Valence bond theory (sigma and pi bonds) and hybridisation. Dipole moment and ionic character in covalent bonds. Bond length. Hydrogen bonding, metallic bond and van der Waals forces. The headings below are its points, in that order.
Three ways it is asked. Recall — the angle in ammonia, the hybridisation in SF₆, which molecule has a co-ordinate bond. Understanding — why water bends further than ammonia, why CO₂ has zero dipole moment although each C=O bond is polar, why AgCl dissolves so poorly for an "ionic" salt. Application — you are given a formula you have never seen, you count bond pairs and lone pairs, and you name the shape and the angle.
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See the plansMole Concept & Stoichiometry Made Simple
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Dalton's postulates and where they fail, the five laws of combination, Avogadro's law and its uses, and every mole calculation the paper can ask, worked step by step.
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