A complete revision and exam practice pack for** SC6a Covalent Bonds**, covering C1.28–C1.31.

Topic Mastery Sheet (PDF) - a comprehensive student reference explaining covalent bonding from the question of why non-metals share rather than transfer electrons. The bonding mechanism is explained clearly: each atom contributes one electron to the shared pair, and the shared pair is attracted to both nuclei simultaneously - this mutual attraction is the covalent bond. Single and double bonds are distinguished with examples. All six required dot and cross diagrams are systematically covered in a reference table: H₂, HCl, H₂O, CH₄, O₂ and CO₂, with key features highlighted for each - number of bonds, lone pairs, which shells are shown. A step-by-step guide to drawing the CO₂ diagram addresses the most commonly misdrawn example: two C=O double bonds with 4 non-bonding electrons on each oxygen and none on carbon. The three molecular models are compared in a table showing exactly what each does and does not show - dot and cross (bond formation), structural formula (connectivity), space-filling (shape and relative size). Atom size order of magnitude (10⁻¹⁰ m) is included. The stretch section introduces VSEPR theory and explains why methane is tetrahedral and water is bent.

Student Exam Practice Sheet (PDF + DOCX) - six questions (12 marks) covering covalent bond formation, molecular formula of N₂, model advantages/limitations, space-filling information, CO₂ dot and cross diagram, and structural formulae for water and methane.

Teacher Answer Key (PDF + DOCX) - full tick-point mark scheme with examiner notes.

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