2 Overview Molecular Shapes VSEPR Model Polarity of Molecules Predicting ShapesEffect of Nonbonding ElectronsPolarity of MoleculesCovalent Bonding
3 Hybrid Orbitals Multiple Bonds Molecular Orbitals sp, sp2, sp3 hybrids containing d orbitalsMultiple Bondssigma (s) & pi (p)localized & delocalizedMolecular Orbitalselectron configurations & bond orderdiamagnetism & paramagnetism
4 Molecular Shapes & VSEPR Shapes defined by bond angleslinear, 180° anglestrigonal planar, 120° anglestetrahedral, 109.5° anglesVSEPRValence Shell Electron Pair Repulsion theoryelectron pairs are arranged symmetrically with maximum separation
5 Two electron pairs180° apartlinear geometry180°•
6 Three electron pairs120° aparttrigonal planar geometry•120°
7 Four electron pairs109.5° aparttetrahedral geometry•109.5°
8 Five electron pairs • angles of 90° and 120° trigonal bipyramidal (TBP) geometry90°•120°
9 Six electron pairsangles of 90°octahedral geometry90°•
10 Geometries Electron pair geometry Molecular Geometry arrangement of electron pairs around a central atomMolecular Geometryarrangement of atoms around a central atomWhen all electron pairs are bonding pairselectron pair geometry = molecular geometryWhen there are unshared electron pairselectron pair geometry ¹ molecular geometry
11 To determine electron pair geometry draw Lewis dot structurecount shared & unshared electron pairs around central atoma multiple bond is counted as only one bonding pair when predicting geometrydetermine electron pair geometry based on the number of electron pairs2 pair = linear3 pair = trigonal planar4 pair = tetrahedral5 pair = trigonal bipyramidal6 pair = octahedral
12 Molecular Geometries with One or More Unshared Pairs Two Pairselectron pair geometry linearbonding pairsnon-bonding pairsmolecular geometry linear
13 Two electron pairsmolecular geometryelectron pair geometry180°•
14 Three Pairs electron pair geometry trigonal planar bonding pairs 3 2 non-bonding pairsmolecular geometry trig. pl bent
15 Three electron pairs • molecular geometry electron pair geometry trigonal planartrigonal planar••bent120°
16 Four Pairs electron pair geometry tetrahedral bonding pairs 4 3 2 non-bonding pairsmolecular geometry tet trig. pyr. bent
17 Four electron pairs • tetrahedral molecular geometry electron pair geometry•trigonal pyramid•109.5°•bent•
18 Five Pairs electron pair geometry trigonal bipyramid bonding pairsnon-bonding pairsmolecular geometry tbp seesaw T-shp. Lin.
19 Five electron pair • 90° electron pair geometry molecular geometry TBP seesaw120°••••T-shaped•linear
20 Six Pairs electron pair geometry octahedral bonding pairs 6 5 4 2 non-bonding pairsmolecular geometry oct sq.pyr. sq. pl. lin.
21 Six electron pairs • electron pair geometry 90° molecular geometry octahedral•square pyramid•••square planar••linear
22 Molecular PolarityMolecules are always non-polar if all covalent bonds are non-polarN2, P4, Cl2Molecules with polar bonds can be polar or non-polarH - Cl polar bond, polar molecularO=C=O two polar bonds but total molecule is non-polar
23 H Cl O C O equal but opposite forces cancel out Þ non-polar molecule d+d-H Clequal but opposite forces cancel out Þ non-polar moleculed+d-d-O C O
24 O H no yes are these dipole moments equal & opposite? is this molecule polar?
25 Cl Cl C Cl Cl yes no are these bond dipole moments equal & opposite? is this molecule polar?
26 H H C Cl Cl no yes are these bond dipole moments equal & opposite? is this molecule polar?
27 Single and Multiple Bonds s (sigma) bondsalways the first bond between two atomssingle bonds are localized between two atomsorbitals from two atoms overlap, allowing electrons to be sharedelectron density is on the internuclear axisC•localized electrons
28 C C p (pi) bonds • • the second & third bonds between two atoms p bond electrons can be delocalized over several atoms to form resonance structureselectron density is above & below the internuclear axiselectron density can move or delocalizeC••electron density above & below--p bondinternuclear axisC
29 Hybridization allows for greater number of bonds types of hybridizationsp mixing of one s orbital & one p orbital¯ 2s p sp psp2 mixing of one s orbital & two p orbitals¯ 2s p sp psp3 mixing of one s orbital & three p orbitals¯ 2s p sp3
30 in sp hybridization in sp2 hybridization in sp3 hybridization the two sp hybrid orbitals form two s bonds with linear geometryremaining two p orbitals form p bondsin sp2 hybridizationthe three hybrid orbitals form three s bonds with trigonal planar geometrythe remaining one p orbital forms a p bondin sp3 hybridizationthe four hybrid orbitals form four s bonds with tetrahedral geometrysp3 hybrid atoms can form no p bonds as they have no unhybridized p orbitals
31 Molecular Orbitals mathematical combinations of atomic orbitals delocalized over whole moleculen atomic orbitals produce n molecular orbitals½ are bonding orbitals and ½ are antibonding orbitalsbond order# bonding electrons - # antibonding electron
32 electron configuration of diatomic, homonuclear molecules s. p. p s s electron configuration of diatomic, homonuclear molecules s * p * p s s * sMO’s from p orbital combinationMO’s from s orbital combination
33 electron configuration of diatomic, homonuclear molecules with interaction of the 2s and 2p orbitals s * p * s p s * srelative positions switched
34 s * p * s p s * s s * p * s p s * s H2 N2 B.O. = 1 B.O. = 3 2 electrons10 electrons
35 s * p * s p s * s s * p * p s s * s He2 O2 B.O. = 0 B.O. = 2 4 electrons12 electrons
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