CHAPTER 2: BONDING AND PROPERTIESOrder: Short vs Long RangeAtomic StructureSlide 4Electronic Structurec02tf01Electron Energy Statesc02f01SURVEY OF ELEMENTSElectron ConfigurationsThe Periodic TableElectronic Configurationsc02tf02ElectronegativityBonding EnergyProperties From Bonding: TmProperties From Bonding : aPrimary BondingIonic Bondingc02f09Ionic bond – metal + nonmetalExamples: Ionic BondingCovalent BondingIonic-Covalent Mixed Bondingc02f11Secondary Bonding (van der Waals)SECONDARY BONDINGc02f15c02tf03Summary: BondingSummary: Primary BondsCHAPTER 2:BONDING AND PROPERTIES•What promotes bonding?•What types of bonds are there?•How does bonding affect material properties? •Much of a material’s behavior can be explained by the phenomena in this chapter.1Order: Short vs Long Range23Atomic Structure•atom – electrons – 9.11 x 10-31 kg protons neutrons•atomic number = # of protons in nucleus of atom = # of electrons of neutral species •A [=] atomic mass unit = amu = 1/12 mass of 12C Atomic wt = wt of 6.022 x 1023 molecules or atoms 1 amu/atom = 1g/molC 12.011H 1.008} 1.67 x 10-27 kg4Atomic Structure•Valence electrons determine the following properties:1) Chemical2) Electrical 3) Thermal4) Optical5Electronic Structure•Electrons have wavelike and particulate properties. –This means that electrons are in orbitals defined by a probability.–Each orbital at discrete energy levels is determined by quantum numbers. Quantum # Designation n = principal (energy level-shell) K, L, M, N, O (1, 2, 3, etc.)l = subsidiary (orbitals) s, p, d, f (0, 1, 2, 3,…, n -1)ml = magnetic 1, 3, 5, 7 (-l to +l)ms = spin ½, -½7Electron Energy States1s2s2pK-shell n = 1L-shell n = 23s3pM-shell n = 33d4s4p4dEnergyN-shell n = 4• have discrete energy states• tend to occupy lowest available energy state.Electrons...9• Why? Valence (outer) shell usually not filled completely.• Most elements: Electron configuration not stable.SURVEY OF ELEMENTSElectron configuration(stable)... ... 1s22s22p63s23p6(stable)... 1s22s22p63s23p63d104s24p6(stable)Atomic # 18...36Element1s1 1Hydrogen1s22Helium1s22s1 3Lithium1s22s24Beryllium1s22s22p15Boron1s22s22p26Carbon...1s22s22p6(stable)10Neon1s22s22p63s111Sodium1s22s22p63s2 12Magnesium1s22s22p63s23p113Aluminum...Argon...KryptonAdapted from Table 2.2, Callister & Rethwisch 3e.10Electron Configurations•Valence electrons – those in unfilled shells•Filled shells more stable•Valence electrons are most available for bonding and tend to control the chemical properties –example: C (atomic number = 6)1s2 2s2 2p2valence electrons11The Periodic Table• Columns: Similar Valence StructureElectropositive elements:Readily give up electronsto become + ions.Electronegative elements:Readily acquire electronsto become - ions.give up 1e-give up 2e-give up 3e-inert gasesaccept 1e-accept 2e-OSeTePo AtIBrHeNeArKrXeRnFClSLi BeHNa MgBaCsRaFrCaK ScSrRb Y12Electronic Configurationsex: Fe - atomic # =26valence electrons1s2s2pK-shell n = 1L-shell n = 23s3pM-shell n = 33d4s4p4dEnergyN-shell n = 41s2 2s2 2p6 3s2 3p63d 6 4s214• Ranges from 0.7 to 4.0,Smaller electronegativity Larger electronegativity• Large values: tendency to acquire electrons.Adapted from Fig. 2.7, Callister & Rethwisch 3e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by Cornell University.Electronegativity15Bonding Energy•Energy – minimum energy most stable–Energy balance of attractive and repulsive termsAttractive energy EANet energy ENRepulsive energy ERInteratomic separation rrAnrBEN = EA + ER = 16• Bond length, r• Bond energy, Eo• Melting Temperature, TmTm is larger if Eo is larger.Properties From Bonding: TmrorEnergyrlarger Tmsmaller TmEo= “bond energy”Energyro runstretched length17• Coefficient of thermal expansion, •  ~ symmetric at ro is larger if Eo is smaller.Properties From Bonding : = (T2-T1)LLocoeff. thermal expansion Llength, Lounheated, T1heated, T2rorlarger  smaller  Energyunstretched lengthEoEoPrimary Bonding•Ionic•Covalent•Metallic18•Bonding involves the valence electrons.•Bonding occurs due to the tendency of the atoms to assume stable electron structures (completely filled outer shells)19• Occurs between + and - ions.• Requires electron transfer.• Large difference in electronegativity required.• Example: NaClIonic BondingNa (metal) unstableCl (nonmetal) unstableelectron + - Coulombic Attraction Na (cation) stableCl (anion) stable21Ionic bond – metal + nonmetal donates accepts electrons electrons Dissimilar electronegativities ex: MgO Mg 1s2 2s2 2p6 3s2 O 1s2 2s2 2p4 [Ne] 3s2 Mg2+ 1s2 2s2 2p6 O2- 1s2 2s2 2p6 [Ne] [Ne]22• Predominant bonding in CeramicsAdapted from Fig. 2.7, Callister & Rethwisch 3e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by Cornell University.Examples: Ionic BondingGive up electrons Acquire electronsNaClMgOCaF2CsCl23C: has 4 valence e-, needs 4 moreH: has 1 valence e-, needs 1 moreElectronegativities are comparable.Covalent Bonding•similar electronegativity  share electrons•bonds determined by valence – s & p orbitals dominate bonding•Example: polymers, GaAs, InSb, SiC, CH4shared electrons from carbon atomshared electrons from hydrogen atomsHHHHCCH424Ionic-Covalent Mixed Bonding% ionic character = where XA & XB are Pauling electronegativitiesionic 70.2% (100%) x e1 characterionic %4)3.15.3( 2Ex: MgO XMg = 1.3XO = 3.5%)100( x 1 e (XA XB)24Metallic Bonding•Metallic bonds have up to 3 valence electrons that are not bound to a specific atom.•They drift throughout the metal forming a “sea of electrons” or “electron cloud”. •The nonvalence electrons and nuclei for the “ion cores”.•The free electrons act as a “glue” to hold the ion cores together.•These are good conductors of heat and charge (electricity).Secondary Bonding (van der Waals)•Interaction between dipoles; dipoles are a separation of charge (+/-).•Weaker forces (10kJ/mol) than primary bonding, yet these bonds still influence