Chapter 8 Part 1 Ionic Bonding Read HW IONIC BLB 2 7 2 8 8 1 8 2 BLB 2 51 53 57 59 65 67 70 71 8 16 22 25 Sup 2 4 5 8 1 electrons traded to form separate ions both have noble gas Know Ionic Bonding Lewis Symbols Nomenclature Lattice energy Na Bonus deadline for Skill Check Tests Approaching When is Exam 1 Data sheet and periodic table in the packet will be provided during the exam Bring pencils student ID and a calculator NO text programmable calculators or wireless devices Cl COVALENT electrons shared between a few nuclei distinct molecules e e METALLIC electrons shared among all nuclei e e sea of electrons Dr Lori Stepan Van Der Sluys 1 Chapter8 Part 1 Dr Lori Stepan Van Der Sluys 2 Chapter8 Part 1 For ionic and covalent bonding Keep track of electrons with Lewis Dot Symbols Knowing the Number of Valence Electrons You Should be Able to Draw These 1 electrons are involved in bonding represent each electron with one dot C C 4 valence electrons 2 S Ne 3s 3p 4 S valence electrons 2 Octet rule elements tend to gain lose or share electrons so as to gain an configuration of 8 electrons Duet for H and He instead of octet Inert gases have 8 valence electrons Dr Lori Stepan Van Der Sluys 3 Chapter8 Part 1 Dr Lori Stepan Van Der Sluys 4 Chapter8 Part 1 IONIC BONDING Ionic Bonding Involves Transfer of to form charged Ionic bond is due to electrostatic attraction Coulomb s Law Q1 charge on 1st atom Q2 charge on 2nd atom d distance between charges Electrons are exchanged to from separate ions with complete Na Cl 1s2 2s2 2p6 1s2 2s2 2p6 3s23p6 Ne Ar complete octets IONIC COMPOUNDS distinct ions crystal lattice strong omnidirectional electrostatic bonds Characteristics 1 low electrical conductivity as solids high as liquids 2 very high melting boiling points 3 hard but brittle 4 soluble only in polar solvents water Dr Lori Stepan Van Der Sluys 5 Chapter8 Part 1 Dr Lori Stepan Van Der Sluys 6 Chapter8 Part 1 Ionic compound a compound that consists of positive and negative ions Naming Inorganic Compounds and Ions See Section 2 8 Metal nonmetal Examples NaCl K2SO4 Mg NO3 2 NH4Cl Ionic compounds have melting points and are brittle many are Molecular compounds compounds consisting of individual molecules All nonmetals or nonmetals plus metalloids Examples HCl H2O CH3COOH NH3 Molecular compounds usually have melting points many are or Dr Lori Stepan Van Der Sluys 7 Chapter8 Part 1 Dr Lori Stepan Van Der Sluys 8 Chapter8 Part 1 Figure 2 26 Be able to fill in information as in the table below Name potassium ion Formula CO32 ammonium ion Figure 2 27 sodium bicarbonate H2SO4 Combine Ca 2 and PO43 Figure 2 28 Dr Lori Stepan Van Der Sluys 9 Cu II and sulfate ion Chapter8 Part 1 Dr Lori Stepan Van Der Sluys 10 Chapter8 Part 1 Formation of ionic salts from the elements is very exothermic Na g Cl g NaCl s H 788 kJ mol BUT Removing an electron from a metal is Na g Na g e H 496 kJ mol And adding an electron to a nonmetal is moderately Cl g e Cl g H 349 kJ mol Overall the process seems like it would be endothermic Why is formation of an ionic salt so favorable The added stability is due to the attraction of the ions for each other The attraction brings the ions close releases energy and forms a Dr Lori Stepan Van Der Sluys 11 Chapter8 Part 1 Strength of Ionic Bond Lattice Energy Lattice Energy measures the strength of the ionic interaction Definition NaCl s Na g Cl g H 786 kJ mol Lattice Energy LE cannot be determined experimentally Use Hess Law and known atomic properties to get the value of the lattice energy Born Haber Cycle By Hess s Law the enthalpy of formation is equal to the sum of the energies of several individual steps Reasons for the stability of ionic compounds is made clear Dr Lori Stepan Van Der Sluys 12 Chapter8 Part 1 Lattice Energy NaCl MgO Salts and Ionic Lattices E 786kJ E 3934kJ ION SIZES Ion sizes are important in ionic bonds Why the big difference E Q1 Q2 d Different salts have different Q s and d s NaCl MgO NaF NaCl NaBr NaI 993oC 801oC 747oC 661oC MgO 2800oC larger anion higher charge Trends Melting point increases as charge Radii Na Cl 0 97 1 81 2 78 2 Mg 2 O 0 66 1 40 2 06 d is for MgO Melting point increases as lattice energy Melting point increases as size SO lattice energy for MgO is more than 4x greater Dr Lori Stepan Van Der Sluys 13 Chapter8 Part 1 Dr Lori Stepan Van Der Sluys 14 Chapter8 Part 1 Which one of the following expresses the correct relationship between the melting points of the 3 ionic solids NaCl MgS and BaS 1 2 3 4 5 NaCl MgS BaS NaCl BaS MgS MgS BaS NaCl MgS NaCl BaS BaS MgS NaCl Dr Lori Stepan Van Der Sluys 15 Chapter8 Part 1
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