Chapter 9 Chemical Bonding I: Lewis Theory

1. Chapter 9Chemical Bonding I: Lewis Theory • Outline • Lewis Theory • Types of Chemical Bonds • Ionic • Born-Haber Cycle • Lattice Energy • Covalent • Electronegativity • Lewis Structures • Bond Energy • Bond Length • Metallic

2. Potential Energy versus Distance

3. Where is the electrostatic potential most energetically favorable?

4. How are bonds classified?

5. How are bonds classified?

6. What happens when sodium metal and chlorine gas are placed in the same reaction flask? Tro: Chemistry: A Molecular Approach, 2/e

8. Lattice Energies

10. Chapter 9: Examples – Formation of Ionic Compounds Calculate the enthalpy of formation of sodium chloride from it’s elements. Given: Na (s) → Na (g) +107.3 kJ/mol Na (g) → Na+(g) + 1 e- +495.8 kJ/mol ½ Cl2 (g) → Cl (g) +122 kJ/mol Cl (g) + 1 e- → Cl- (g) -348.6 kJ/mol Na+ (g) + Cl- (g) → NaCl (s) -787 kJ/mol

12. Chapter 9: Examples – Formation of Ionic Compounds Calculate the energy released in kJ/mol when sodium iodide is formed. Na (s) + ½ I2 (s) → NaI (s) The energy of vaporization of elemental sodium is 107 kJ/mol. The ionization energy of sodium is 486 kJ/mol. The sum of the enthalpies of dissociation and vaporization of elemental iodine is 214 kJ/mol and the electron affinity of iodine is -295 kJ/mol. The lattice energy of sodium iodide is -704 kJ/mol.

13. Chapter 9: Examples – Formation of Ionic Compounds Calculate the energy released in kJ/mol when lithium hydride is formed. The heat of vaporization of elemental lithium is 161 kJ/mol, the ionization energy of lithium is 520 kJ/mol. The dissociation energy of hydrogen gas is 436 kJ/mol and the electron affinity of a gaseous hydrogen atom is -73 kJ/mol. The lattice energy of lithium hydride is -917 kJ/mol.

14. Chapter 9: Examples – Formation of Ionic Compounds Determine the energy of formation of magnesium bromide. Given: Mg (s) → Mg (g) +147.7 kJ/mol Mg (g) → Mg+(g) + 1 e- +737.7 kJ/mol Mg+(g) → Mg2+ (g) + 1 e- +1,450.7 kJ/mol Br2 (g) → 2 Br (g) +193 kJ/mol Br (g) + 1 e- → Br- (g) -325 kJ/mol Mg2+ (g) + 2 Br- (g) → MgBr2 (s) -2,440 kJ/mol

15. How does atomic size affect lattice energy?

16. How does ionic charge affect lattice energy?

21. Bond Polarity NaCl HCl Cl-Cl

23. ENCl = 3.0 3.0 − 3.0 = 0 Pure Covalent ENCl = 3.0 ENH = 2.1 3.0 – 2.1 = 0.9 Polar Covalent ENCl = 3.0 ENNa = 0.9 3.0 – 0.9 = 2.1 Ionic Bond Polarity Tro: Chemistry: A Molecular Approach, 2/e

27. Bond length - the optimum distance between nuclei in a covalent bond.

30. Chapter 9: Examples – Bond Energy Approximate the ΔHrxn for the production of ammonia by the Haber process: N2 (g) + 3 H2 (g)  2 NH3 (g)

31. Chapter 9: Examples – Bond Energy Approximate the ΔHrxn for the combustion of methane: CH4 (g) + 2 O2 (g)  CO2 (g) + 2 H2O (g)

32. Chapter 9: Examples – Bond Energy Approximate the ΔHrxn for the halogenation of acetylene gas: C2H2 (g) + 2 Cl2 (g)  C2H2Cl4 (g)

33. Metal Bonding