MOLECULAR 1 MOLECULAR GEOMETRY VSEPR …

1 Page 11 MOLECULARGEOMETRYMOLECULARMOLECULARGEOME TRYGEOMETRY2 VSEPRVSEPR VValence alence SShell hell EElectronlectronPPair air RRepulsion theory. Most important factor inMost important factor indetermining GEOMETRY isdetermining GEOMETRY isrelative repulsionrelative repulsionbetween electron electron VSEPRVSEPR VValence alence SShell hell EElectronlectronPPair air RRepulsion theory. Most important factor inMost important factor indetermining GEOMETRY isdetermining GEOMETRY isrelative repulsionrelative repulsionbetween electron electron theshape thatminimizes theelectron theadopts theshape thatshape thatminimizes theminimizes theelectron pairelectron GEOMETRYMOLECULAR GEOMETRYMOLECULAR GEOMETRY4 HHHH tetrahedral109 C4120 planar trigonalFFBF3180 linear2 GeometryExampleNo. of e- PairsAround CentralAtomF Be F5 HHHH tetrahedral109 C4120 planar trigonalFFBF3180 linear2 GeometryExampleNo.

2 Of e- PairsAround CentralAtomF Be F6 HHHH tetrahedral109 C4120 planar trigonalFFBF3180 linear2 GeometryExampleNo. of e- PairsAround CentralAtomF Be FPage 27 HHHH tetrahedral109 C4120 planar trigonalFFBF3180 linear2 GeometryExampleNo. of e- PairsAround CentralAtomF Be F8 Structure Determinationby VSEPRS tructure DeterminationStructure Determinationby VSEPRby VSEPRA mmonia, NHAmmonia, NH331. Draw electron dot structure1. Draw electron dot structure2. Count BP s and LP s = 42. Count BP s and LP s = 43. The 4 electron pairs are at the3. The 4 electron pairs are at thecorners of a corners of a pair of electronsin tetrahedral positionNH HHN9 Structure Determinationby VSEPRS tructure DeterminationStructure Determinationby VSEPRby VSEPRA mmonia, NHAmmonia, NH33 There are 4 electron pairs at theThere are 4 electron pairs at thecorners of a of a pair of electronsin tetrahedral positionNH HHNH HHNThe ELECTRON PAIR GEOMETRY The ELECTRON PAIR GEOMETRYELECTRON PAIR GEOMETRY is , NHAmmonia.

3 NH33 The electron pair GEOMETRY is electron pair GEOMETRY is Determinationby VSEPRS tructure DeterminationStructure Determinationby VSEPRby VSEPRHHH lone pair of electronsin tetrahedral positionNThe MOLECULAR GEOMETRY thepositions of the atoms is The MOLECULAR GEOMETRYMOLECULAR GEOMETRY the thepositions of the atoms is positions of the atoms is Determinationby VSEPRS tructure DeterminationStructure Determinationby VSEPRby VSEPRW ater, HWater, H22OO1. Draw electron dot structure1. Draw electron dot structureHHOHHOThe electron pairgeometry electron pairThe electron pairgeometry isgeometry HOH 2. Count BP s and LP s = 42. Count BP s and LP s = 42. Count BP s and LP s = 43. The 4 electron pairs are at thecorners of a The 4 electron pairs are at the3. The 4 electron pairs are at thecorners of a of a Determinationby VSEPRS tructure DeterminationStructure Determinationby VSEPRby VSEPRW ater, HWater, H22 OOHHOHHOThe electron pairgeometry isTETRAHEDRALThe electron pairThe electron pairgeometry isgeometry isTETRAHEDRALTETRAHEDRALThe moleculargeometry molecularThe moleculargeometry isgeometry HOH Page 313 Structure Determinationby VSEPRS tructure DeterminationStructure Determinationby VSEPRby VSEPRF ormaldehyde, CHFormaldehyde, CH22OO1.

4 Draw electron dot structure1. Draw electron dot structureThe electron pairgeometry is PLANARTRIGONAL with 120obond electron pairThe electron pairgeometry is GEOMETRY is PLANARPLANARTRIGONAL TRIGONAL with 120with 120oobond angles. CHHO CHHO 2. Count BP s and LP s = 32. Count BP s and LP s = 32. Count BP s and LP s = 33. There are 3 electron pairs are at thecorners of a planar There are 3 electron pairs are at the3. There are 3 electron pairs are at thecorners of a planar of a planar Determinationby VSEPRS tructure DeterminationStructure Determinationby VSEPRby VSEPRF ormaldehyde, CHFormaldehyde, CH22 OOThe electron pairgeometry is PLANARTRIGONALThe electron pairThe electron pairgeometry is PLANAR GEOMETRY is PLANARTRIGONALTRIGONALThe moleculargeometry is also molecularThe moleculargeometry is also planargeometry is also CHHO CHHO 15 Methanol, CHMethanol, CH33 OHOHD efine bond angles 1 andDefine bond angles 1 and22 Angle 1 = 109 Angle 1 = 109ooAngle 2 = 109 Angle 2 = 109ooIn both cases the atom In both cases the atom is surrounded by is surrounded by 4 electron electron DeterminationStructure Determinationby VSEPRby VSEPRHH109 109 H C O H16 Structure Determinationby VSEPRS tructure DeterminationStructure Determinationby VSEPRby VSEPRA cetonitrileAcetonitrile, CH.

5 CH33 CNCN HHH C CN180 109 H-C-H = 109o C-C-N = 180oH-C-H = 109H-C-H = 109oo C-C-N = 180C-C-N = 180ooOne C is surrounded by 4 electron lumps and the other by 2 lumps One C is surrounded by 4 electronOne C is surrounded by 4 electron lumps and the other by 2 lumps lumps and the other by 2 lumps Define unique bond anglesDefine unique bond anglesDefine unique bond angles17 PhenylalaninePhenylalanine, an amino acid, an amino acidCCCCCCCCCHHHHHHHHOOHNHH2345118 PhenylalaninePhenylalaninePhenylalanineP age 419 Structures withCentral Atomswith More Thanor Less Than 4 Electron PairsStructures withStructures withCentral AtomsCentral Atomswith More Thanwith More Thanor Less Than 4or Less Than 4 Electron PairsElectron Pairs20 Central Atoms With FewerThan 4 Electron PairsCentral Atoms With FewerCentral Atoms With FewerThan 4 Electron PairsThan 4 Electron PairsOften occurs with Group 3A elementsOften occurs with Group 3A elementsand with those of 3rd period andand with those of 3rd period boronConsider boron trifluoride trifluoride, BF, BF3321 Boron CompoundsBoron CompoundsBoron CompoundsConsider boronConsider boron trifluoride trifluoride.

6 BFBF33F FFB GEOMETRY describedGeometry describedas as planarplanartrigonaltrigonalThe B atom is surrounded byonly 3 electron angles are 120oThe B atom is surrounded byThe B atom is surrounded byonly 3 electron 3 electron angles are 120 Bond angles are 120oo22 Compounds with 5 or 6 PairsAround the Central AtomCompounds with 5 or 6 PairsCompounds with 5 or 6 PairsAround the Central AtomAround the Central Atom23 FFFFFT rigonal bipyramid120 90 PFFFFFT rigonal bipyramid120 90 P5 electron pairs5 electron pairsCompounds with 5 or 6 PairsAround the Central AtomCompounds with 5 or 6 PairsCompounds with 5 or 6 PairsAround the Central AtomAround the Central Atom24 Compounds with 5 or MorePairs Around the Central AtomCompounds with 5 or MoreCompounds with 5 or MorePairs Around the Central AtomPairs Around the Central AtomFFFFFT rigonal bipyramid120 90 PFFFFFT rigonal bipyramid120 90 PFFFFFFO ctahedron90 90 SFFFFFFO ctahedron90 90 S5 electron pairs5 electron pairs6 electron pairs6 electron pairsPage 525 Number of valence electrons =Number of valence electrons = Central atom = Central atom = Dot structureDot structureSulfur Tetrafluoride, SF4 SulfurSulfur Tetrafluoride Tetrafluoride, SF, SF4426 Number of valence electrons = 34 Number of valence electrons = 34 Central atom = S Central atom = S Dot structureDot structureFFFF SSulfur Tetrafluoride, SF4 SulfurSulfur Tetrafluoride Tetrafluoride, SF, SF4427 Number of valence electrons = 34 Number of valence electrons = 34 Central atom = SCentral atom = SDot structureDot structureElectron pair GEOMETRY = ?

7 Electron pair GEOMETRY = ?FFFF SSulfur Tetrafluoride, SF4 SulfurSulfur Tetrafluoride Tetrafluoride, SF, SF4428 Number of valenceNumber of valenceelectrons = 34electrons = 34 Central atom = S Central atom = S Dot structureDot structureElectron pair geometryElectron pair GEOMETRY == trigonal bipyramid trigonal bipyramid(because there are 5(because there are 5pairs around the S)pairs around the S)FFFF SSulfur Tetrafluoride, SF4 SulfurSulfur Tetrafluoride Tetrafluoride, SF, SF44 FFFF 120 90 S29 Lone pair is in the equatorLone pair is in the equatorbecause it requires morebecause it requires SFFFF SFFFF 120 90 SFFFF 120 90 SSulfur Tetrafluoride, SF4 SulfurSulfur Tetrafluoride Tetrafluoride, SF, SF44