ch09---intermediate-type-of-bonding.ppt

New Way Chemistry for Hong Kong A-Level Book 11Chapter 9Intermediate Type of Bonding9.1Incomplete Electron Transfer in Ionic Compounds9.2Electronegativity of Elements9.3Polarity of Covalent BondsNew Way Chemistry for Hong Kong A-Level Book 12Born-Haber Cycle for the formation of sodium chlorideHlattice can be found from the Born-Haber CycleExptal value of Hlattice 9.1 Incomplete Electron Transfer in Ionic Compounds(SB p.234)Theoretical Values of Lattice EnthalpyNew Way Chemistry for Hong Kong A-Level Book 13Another way of getting the value of Hlattice Assuming perfect ionic model1.Ions are perfect spheres with uniform charge distribution.2.The cations and anions are in contact with each other and with electrostatic interactions in between.9.1 Incomplete Electron Transfer in Ionic Compounds(SB p.234)New Way Chemistry for Hong Kong A-Level Book 14Another way of getting the value of Hlattice The force(F)between two point charges q1 and q2 separated by a distance R is given by:R_q2q1+Hlattice=work done when the ions are allowed to be brought from infinite separation to the internuclear distance in the ionic latticewhere r is the normal internuclear distanceTheoretical value of Hlattice 9.1 Incomplete Electron Transfer in Ionic Compounds(SB p.234)New Way Chemistry for Hong Kong A-Level Book 15Increasing polarization of a negative ion by a positive ionPolarization/Distortion of electron cloud=Covalent character in ionic bond9.1 Incomplete Electron Transfer in Ionic Compounds(SB p.236)Polarizing power of cationpolarizability of anionNew Way Chemistry for Hong Kong A-Level Book 16Polarizing power of a cationincreases as its charge density(charge/volume ratio)increases.polarizing power:Al3+Mg2+Na+andLi+Na+K+9.1 Incomplete Electron Transfer in Ionic Compounds(SB p.236)Increasing polarization of a negative ion by a positive ionPolarizing power of cationNew Way Chemistry for Hong Kong A-Level Book 17Polarizability of a anionincreases as its size increases.polarizability:I-Br-Cl-andS2-O2-Increasing polarization of a negative ion by a positive ion9.1 Incomplete Electron Transfer in Ionic Compounds(SB p.236)polarizability of anionNew Way Chemistry for Hong Kong A-Level Book 18Electronegativity is defined as the relative tendency of an atom to attract a bonding pair of electrons towards itself.XYX:Y9.2 Electronegativity of Elements(SB p.238)Electronegativity values of some representative elementsNew Way Chemistry for Hong Kong A-Level Book 19Bond Polarization9.3 Polarity of Covalent Bonds(SB p.239)a pure covalent bonda polar covalent bondNew Way Chemistry for Hong Kong A-Level Book 110Relationship between the type of bond and difference in electronegativity between two bonded atomsBondDifference in electronegativity between the two bonded atomsType of bondCl-ClCl-CCl-HF-Li3.0-3.0=03.0-2.5=0.53.0-2.1=0.94.0-1.0=3.0CovalentPolar covalentPolar covalentIonic9.3 Polarity of Covalent Bonds(SB p.239)New Way Chemistry for Hong Kong A-Level Book 111Relationship between bond nature and difference in electronegativity between bonded atoms.9.3 Polarity of Covalent Bonds(SB p.240)New Way Chemistry for Hong Kong A-Level Book 112Polarity of Molecules(Debye,D)=q x d9.3 Polarity of Covalent Bonds(SB p.240)How polar is the molecule?represented by dipole moment()New Way Chemistry for Hong Kong A-Level Book 1139.3 Polarity of Covalent Bonds(SB p.241)The effect of an electric field on polar moleculesNew Way Chemistry for Hong Kong A-Level Book 114The effect of an electric field on non-polar molecules9.3 Polarity of Covalent Bonds(SB p.241)New Way Chemistry for Hong Kong A-Level Book 115Non-polar Molecules9.3 Polarity of Covalent Bonds(SB p.242)ShapeMoleculeCancelling out of dipole momentsLinearTrigonal planarTetrahedralNew Way Chemistry for Hong Kong A-Level Book 1169.3 Polarity of Covalent Bonds(SB p.242)Non-polar Molecules(Contd)ShapeMoleculeCancelling out of dipole momentsTrigonal bipyramidalOctaherdralNew Way Chemistry for Hong Kong A-Level Book 117Polar Molecules9.3 Polarity of Covalent Bonds(SB p.243)ShapeMoleculeDipole moment of individual polar bondsNet resultant dipole momentV-shaped(or bent)Trigonal pyramidalTetrahedralNew Way Chemistry for Hong Kong A-Level Book 118Use of Dipole Moments9.3 Polarity of Covalent Bonds(SB p.243)New Way Chemistry for Hong Kong A-Level Book 119Effect of a Non-uniform Electric Field on polar and Non-polar Liquid9.3 Polarity of Covalent Bonds(SB p.244)Solvents showing a marked deflectionSolvents showing no deflectionTrichloromethane,CHCl3Ethanol,CH3CH2OHPropanone Water,H2OTetrachloromethane,CCl4CyclohexaneBenzeneNew Way Chemistry for Hong Kong A-Level Book 120