Chemical Bonding What holds things together?Slide 2BondingBonding…Write out the electron configuration for the following atoms and ions:Slide 6What about the distance between the atoms in a bond?Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Bond EnergySlide 16Slide 17Slide 18Slide 19Show the direction of electron migration ( ) in the following.Slide 21Slide 22Slide 23Chemical BondingWhat holds things together?PGCC CHM 101 SinexChlorides of Period 2compoundLiCl BeCl2BCl3CCl4NCl3OCl2Cl2melting point610 415 -107 -23 -40 -121 -102Chlorides of Period 3compoundNaCl MgCl2AlCl3SiCl4PCl3SCl6Cl2melting point801 714 193 -69 -112 -51 -102Let’s examine the melting point of compounds across two periods.What is the trend?lowhighConductivity - high Conductivity - lowCRC Handbook of Chemistry and Physics, 1995Bonding Can we explain the melting point behavior across a period?•involves the valence electrons or outermost shell (or highest shell) electrons•for group A elements - the group number tells how many valence electronsHow many valence electrons on N?Group 5A – 5 valence electronsBonding… •Lewis dot structures show the valence electrons around at atom and for most molecules and compounds a complete octet for the elements•most monatomic ions have an electron configuration of noble gases NAlF+ e- F1s22s22p51s22s22p6 NeWrite out the electron configuration for the following atoms and ions:HeNeArKrH-Ca+2O-2Br-Which noble gas is isoelectronic with each ion?Na ClNaCl+-electron transferand the formation of ionsThis is the formation of an ionic bondionic bond.ClClCl2This is the formation of a covalent bondcovalent bond.sharing of a pair of electronsand the formation of moleculesWhat about the distance between the atoms in a bond?NaCl Na+ Cl- d = 281 pmCl2 Cl-Cl d = 199 pmWhat property can be used to tell when a bond will ionic or covalent?ioniccovalentHCl H2O CH4MgO CaCl2Na2SDraw the Lewis dot structures for the following compounds:Some exceptions to the Octet RuleBF3PCl5SF6ElectronegativityChlorides of Period 2compoundLiCl BeCl2BCl3CCl4NCl3OCl2Cl2EN2.2 1.6 1.1 0.6 0 0.6 0Chlorides of Period 3CompoundNaCl MgCl2AlCl3SiCl4PCl3SCl6Cl2EN2.2 1.9 1.6 1.3 1.0 0.6 0large difference small differenceThe electronegativity difference - EN = ENhigher – EN lowerUsing electronegativities to determine bond typeEN > 1.7 ionic bond - transferEN < 1.7 covalent bond - sharingSo we have a range of electronegativity difference of 0 to 1.7 for sharing an electron pair.Is the sharing of electrons in molecules always equal?X YEN = 0X YEN = 0.3X YEN = 0.6X YEN = 0.9X YEN = 1.2ENY > ENXWhich element is more electronegative?non-polar bondincreasing polarity of bondpolar bond0 < EN < 1.7Direction of electron migrationBF3 – a planar molecule Ball & stickBFSpace-filledElectrostatic potential mapstopsidenegativepositiveSpartan ‘022.04.0More sharing examplesO2N2OON NO O OON N N NN Ndouble bond (2 pairs)triple bond (3 pairs)Share until octet is complete.octet completeBond EnergyF2 single bond BE = 142 kJ/moleO2 double bond BE = 494N2 triple bond BE = 942X2 + energy  X + Xincreasing bond strengthIs breaking a bond an endothermic or exothermic process? http://wulfenite.fandm.edu/Data%20/Table_6.htmlNH3NHHHNHHHH+NH4+NH3 + H+  NH4+coordinate covalent bond(the pair of electrons from the same atom)normal covalent bond(each atom supplies an electron)Some more sharing examplesType of bond? – I, PC, or NCTiO2CH4NaICS2CO2KClAlCl3CsF HBrUsing the EN trends to predict bond type105Db107BhIncreasing ENIncreasing ENNO RbF FeS H2SModified from http://www.cem.msu.edu/~djm/cem384/ptable.htmlDraw the Lewis dot structuresCO2H3O+COH2CONH2-HCN(C in center)Show the direction of electron migration ( ) in the following.C – HH – FC = OC – ClRank the bond polarity (1-most … 3-least)As-H N-H P-HHere is the electrostatic potential map for H2CO.Show the electron migration on this planar molecule.C OHHHow is this molecule different than BF3?blue – positive red - negativeionic covalentvalence electronsComparison of Bonding Typessharing of electronstransfer of electronsionsmoleculesEN > 1.7 EN < 1.7high mplow mpmolten salts conductivenon-conductiveBonding spectrum100% covalent 100% ionicA+ B-A B A BIncreasing ENIncreasing