Structure and Bonding — A/L Chemistry

What must I remember about Structure and Bonding?

• Primary bonding types: Ionic (electrostatic attraction between ions), Covalent (shared electron pairs), and Metallic (positive cations in a delocalized sea of electrons).
• VSEPR theory states that electron pairs around a central atom repel each other to minimize electrostatic repulsion: lone pair-lone pair > lone pair-bond pair > bond pair-bond pair.
• Bond polarity arises from electronegativity differences; a molecule with polar bonds is non-polar overall if its dipole moments cancel symmetrically (e.g. CCl₄ vs CHCl₃).
• Intermolecular forces govern physical properties: London dispersion forces (all species, increases with polarizability/molar mass), dipole-dipole interactions, and hydrogen bonding.
• Hydrogen bonding requires a hydrogen atom covalently bonded directly to a small, highly electronegative atom (N, O, or F) with at least one lone pair.

Test yourself (1 minute)

1. Common molecular geometries

   BeCl₂ (linear, 180°), BF₃ (trigonal planar, 120°), CH₄ (tetrahedral, 109.5°), NH₃ (trigonal pyramidal, 107°), H₂O (bent, 104.5°), PCl₅ (trigonal bipyramidal), SF₆ (octahedral, 90°).

2. Dative (coordinate) covalent bonding

   shared pair of electrons provided entirely by one donor atom with a lone pair (e.g., NH₄⁺, H₃O⁺).

3. Why does graphite conduct electricity when diamond does not?

   Graphite conducts electricity parallel to layers due to delocalized π electrons, whereas diamond is an electrical insulator.

Practise Structure and Bonding questions today

Source: NIE G.C.E. (A/L) Chemistry Syllabus (Unit 2)

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Grade 12 · Term 1