Slide 1Formation of BondsRepresenting Electrons Available for BondingSample ProblemTypes of BondsTypes of BondsTypes of BondsStability of Ionic BondsSample ProblemModel explains Properties of Ionic CompoundsTypes of BondsCovalent BondsMultiple Covalent BondsSlide 14Electronegativity (EN)Extent of Sharing in Covalent BondsSharing of Electrons in Covalent Bonds Cont’dDipolesSlide 19Lewis StructuresSlide 21Slide 22Drawing Lewis Structures 1) NO2+Slide 24Slide 25Sample ProblemsSample ProblemSample ProblemsSample ProblemsSample ProblemsResonanceResonanceResonanceSample ProblemsSample ProblemsSample ProblemsSample ProblemsResonanceSlide 39Polyatomic Ions & AcidSlide 41Polyatomic Ions & AcidClass Practice ProblemsSlide 44Slide 45Slide 461Bonding &Lewis StructuresChapter 8Chemistry the Central Scienceby: Brown, Lemay, Bursten, Murphy & WoodwardPresented by: Dr. Stacey GuldeFormation of BondsOctet Rule – when atoms form a compound they will gain, lose or share electrons to obtain a noble gas electron configurationMost noble gasses have _____ valence electrons•Except He, it has ____ valence electrons823Representing Electrons Available for BondingElectron Dot Symbols – represents valence electronsWant to be symmetrical•Specific order for showing electrons:Single electrons are available for bonding1234 567 8X4Sample ProblemGive the electron dot symbols for Nitrogen and indicate the number of electrons available for bonding:Valence electrons = Bonding electrons = N5 e’sClicker 8.1:3 e’sTypes of BondsThere are 3 major categories of bonds that hold atoms together1. Metallic2. Ionic3. Covalenti. Polarii. Non-polar5Video of Bond typesOnly watch the first1:30minsTypes of Bonds1. Metallic – sharing of electrons, in a metal elementMetals lose electrons easily (low IE),but don’t gain (low neg. EA)•Shares electrons by pooling into a “sea” Electrons from 1 Na atom are attractedto their own nucleus, & nucleus of other Na atoms•Shared electrons are de-localized (moving freely throughout the metal)6Types of Bonds2. Ionic bonds – transfer of electronsin ionic compoundsMetals lose electrons (low IE),non-metals gain (high neg. EA)•Each obtaining a noble gas electron config.•Charged IONS held together strongly in 3-D solidEx: NaCl7+ Cl: [Ne]2s2 2p5 Na+: [Ne]+ Cl-: [Ne]2s2 2p6 Cl+NaCl-Na+TransferNa:[Ne]3s1[Ar]+Stability of Ionic BondsLattice energy – energy required to separate one mole of a solid ionic compound into gaseous ionsThe more pos. the more stable the compoundCoulomb’s Law - potential energy (E) b/t 2 ionsAs charge increases, lattice energy increasesAs radius distance decreases, lattice energy increases8Lattice energy = 786 kJ/mol(Endothermic)Q = ion charged = distance b/t ions (aka. atomic radius)k = proportionality constant (8.99x109 Jm/C2)(g)Cl(g)NaNaCl(s)-221dQQE k_______ < _______ < ______ lowhighSample ProblemRank the lattice energies of CaCl2, MgCl2 & NaCl from lowest to highest.9Charges:Distance (size):Ca less ECa > MgNaClCaCl2MgCl2More ELess(Stable)(+2)(-1) (+2)(-1) (+1)(-1)221dQQE kModel explains Properties of Ionic CompoundsIonic Solids are hard (don’t dent), rigid (don’t bend) & brittle (crack w/o deforming)Due to STRONG IONIC bonds holding IONS in a specific positions•If enough pressure is applied, ions of like charges come in contact and repel10Types of Bonds3. COVALENT bonds – sharing electronsin molecular compoundsNon-metals hold onto their electrons(high IE) BUT attract other electrons(high neg. EA)Electrons of 1 atom (Cl) attracted to nucleus of other atom (Br)•Shared electrons are localized (between the atoms)1112Covalent BondsTalk about electrons in terms of pairsBonding pairs – are shared electrons•Represented as linesNonbonding pairs – are unshared or lone pairs•Represented as dotsFHF+HF HShares13Multiple Covalent BondsAtoms can share many pairs of electronsSingle bond – share 2 electronsDouble bond – share 4 electronsTriple bond – share 6 electronsMore electrons in the bond = strong bondsStrong bonds = short bondsOONN123Atoms capable of having multiple bonds must have multiple electrons available for bondingHydrogen & Halogens: ___ available •Only single bondsOxygen: ___ available •Prefer w/2 bondsNitrogen: ___ available•Prefer w/3 bondsCarbon: ___ available•Prefer w/4 bonds14HF1234NOCCapable of anycombo of bonds(1, 2, 3 or 4)XXXXXXXXXXPossible bond distributions:Electronegativity (EN)Electronegativity (EN) – a BONDED atoms ability to attract electrons in a bondValues range from 0.7 – 4.0 •High values, are better at attracting electrons (F=4.0)•Small atoms have high Zef & strongly pull electronsTrend:•Increases1516Extent of Sharing inCovalent BondsPolarity – describes electron sharingBased on ELECTRONEGATIVITY1. Nonpolar COVALENT bonds – equal sharingPresent b/t: Identical nonmetal atoms•H2 Electron cloud – space likely to find electronsH2.1H2.1Electron cloud= 0 No shiftSharing of Electrons inCovalent Bonds Cont’dH2.1F4.0= 1.9Shift!2. Polar COVALENT bonds – unequal sharingPresent b/t: different non-metal atomsDue to: unequal attraction for electrons (electronegativity)•Results in an: electron cloud shiftEx: HFIn the molecule HF, which atom will have more electron cloud around it?A. HB. F18DipolesIn an HF molecule, more electrons are around F, thus, this end develops a partial negative chargeThe hydrogen end develops a partial positive chargeExistence of partial charges is called a dipoleUse ____________ to indicate direction of dipolepartial pos.(+)partial neg.(-)F H19The greater the electronegativity distance between two atoms, the more polar the bondClicker 8.2: Which bond is more polar?CO NO FODipoles2.5  3.5= 1.03.0  3.5= 0.54.0  3.5= 0.520Lewis StructuresLewis structures – shows 2-D covalent bondingShows how atoms are connectedMust:1. Use valence electrons!2. Usually have an octet when done!•(Noble gas configuration)21Exceptions to Octet Rule1. Molecules with an odd number of electrons2. Incomplete octet – atoms with less than an octetElectronegativity is too low to obtain more electronsBeryllium: –Has 2 available electrons, stable w/4 electronsBoron: –Has 3 available electrons, stable w/6 electronsNOBeB22Exceptions to Octet Rule3.