(©2007, François G. Amar, All rights reserved)

Summary for Week 11

Quiz on Friday, November 14

Reading:

For this week: Chapter 7.2-7.4, 8.1 - 8.8

A look ahead: Chapter 9

OWL Assignment for Week 11:

Chapter 6(end) & 7(beginning) assignment (called Ch 8 in OWL) electron configurations and chemical periodicity: due November 18, 2007

Homework problems:

Chapter 7: 7.6, 7.7, 7.10, 7.14, 7.19, 7.20, 7.25, 7.27, 7.35

Beginning of Chapter 8: 8.2, 8.7, 8.14, 8.17, 8.23, 8.27, 8.32, 8.33, 8.35, 8.39

End of Chapter 8: 8.43, 8.45, 8.47, 8.48, 8.53, 8.58, 8.60, 8.61, 8.66

Key concepts and equations:

Chapter 7:

Screening and effective nuclear charge Z_eff=Z-S

Sizes of atoms and ions

Cations are smaller than neutral parents

		Anions are larger than neutral parents

Isoelectronic series

Ionization energies, I₁,I₂ etc

Electron affinity

Chapter 8:

Electronegativity concept (see pp 312-313)

         Ionic, covalent and metallic bonds      

Lewis symbols and the octet rule
      
      Ionic bonding and lattice energy
            
      		Eionic = kQ1Q2/d        (k=8.99x109 J-m/C2)
      
         Electron configurations of common atomic ions obey the octet rule
            

Covalent bonding (sharing electrons): electron pair bond.
  
	
	Drawing Lewis dot structures for molecules
      
	Bond polarity (unequal sharing)

    Dipole moment
          µ=Qr       
	          if Q is in C and r in m, then µ is in C-m
			1 D or 1 Debye = 3.34x10-30 C-m
            look at Sample exercise 8.5 on page 315 of BLB
      
	Electronegativity
      
	Formal charge (the limiting case of perfect sharing) 
		the Lewis structure with smaller formal charges is preferred
	Example of CO2 molecule given here
      
	Resonance structures
      
	Exceptions to the octet rule 

odd number of electrons
(>8) 3rd row elements
(<8) B and Be

      
	Bond strength and bond length
      
	Bond enthalpies and estimating enthalpies of reaction
      
      	  Hrxn  ~    Sum(bond enthalpies of bonds broken) 

-   Sum(bond enthalpies of bonds formed)