BONDING & SHAPES | AS AQA Physical Chemistry

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and anions. Different compounds have different lattices Properties: Dissolves in water (water = polar) Conducts electricity when molten (charged particles free to move and carry charge) • High melting points (strong ionic bonds) Can break into fragments →when hit, layers of alternating charges becomes distorted, similar charges repels, breaks apart into fragments ● Diagram: TYPES OF SOLID STRUCTURE: Na cr MACROMOLECULAR (giant covalent) A lattice of many atoms each with multiple covalent bonds Properties: high melting and boiling point, insolubility in water, can be rigid, can conduct electricity e.g. Diamond, Graphite A lattice of positive metal ions and a sea of delocalised electrons Properties: • High melting and boiling points Insoluble in water Good conductivity when solid and molten ● Diagram: METALLIC solid metal e.g. methane Properties: low melting & boiling points (weak VDW forces), poor insolubility in water, poor conductors MOLECULAR 0 sea of delocalised electrons metal cation 3.1.3.5 Shapes of simple molecules and ions ● Electrons will try to stay as far apart from each other as possible ● Lone pairs held closer to nucleus → repel each other more as they're closer ● Trend in repulsion strength (most to least): LP-LP, LP-BP, BP- WEAK INTERMOLECULAR FORCES STRONG COVALENT BONDS [INTRAMOLECULARY NUM OF BONDING PAIRS 2 3 NUM OF LONE PAIRS 0 1 2 3 0 NAME Linear Bent Bent Linear Trigonal Planar BOND ANGLE 180 <120 104.5 180 120 F DIAGRAM -Be < 120° Xe I B. F F e.g. CO₂2 SnCI, H₂O XeF2 BF3 1 2 0 1 2 Triangular Pyramid T-Shaped Tetrahedral Seesaw Square Planar 107 90, 180 109.5 90, 120, 180 90 <90% H <120° " 90° H 1 с 107⁰ <90° X X₂ ...H H X NH3 CIF 3 CH4 SF4 PtCl4 5 6 0 1 0 Trigonal Bipyramid Square Pyramidal Octahedral 90 and 120 90 90 A 90° F B B 90° 120⁰ FISIF 90° -B CIF5 PC15 SF6 3.1.3.6 Bond polarity Polarity: Polar bonds caused by differences in electronegativities ● Electronegativity → The ability to attract electron pairs in a covalent bond ● Most electronegative element →→ Fluorine 3.1.3.7 Forces between molecules Van der Waals: ● Electron clouds around molecules → constantly in motion ● Partial charges rapid changes Induced Dipoles: ● Partial charge of one molecule can push away the electrons in another ● Meaning temporary dipoles induce dipoles in nearby molecules ● VDW strength depends on the number of electrons in a molecule ● more electrons → much stronger VDW forces Larger fluctuation in electron density Leads to larger temporary dipoles and stronger dipole-dipole interactions ● Dipole-Dipole: Exists between 2 permanently polar molecules delta +tive attracts delta -tive of another molecule Molecules will line up throughout a liquid or solid ● Second strongest molecular interaction Only found between polar molecules ● Hydrogen Bonds: Found when H is bonded w O₂ N₂ or F2 ● Strong permanent dipole dipole, H₂O Small Atoms →→ High Charge Density → Can form strong bonds w any highly delta -tive charges atoms ●