1. Chemical Bonding I www.chem.hawaii.edu/Bil301/welcome.html
CHEMISTRY 161
Chapter 9
Chemical Bonding I

2. Periodic Table of the Elements
ns2np6
ns1
ns2
chemical reactivity - valence electrons

3. THE OCTET RULE ns2np6 atoms combine to form compounds
in an attempt to obtain a stable
noble gas electron configuration
ns2np6
isoelectronic

4. A + B → AB 1. ELECTRON FULLY TRANSFERED IONIC BONDING NaCl
2. ELECTRON SHARING
COVALENT BONDING
HCl

5. represents one valence electron
LEWIS MODEL OF BONDING
LEWIS
DOT SYMBOL
DOT
represents one valence electron H.
Gilbert Lewis
( )

6. . . . . . . . . . .
with the exception of He, the main group number represents number of ‘dots’

7. IONIC BONDING Na electron transfer Ne core implied in symbol
1s22s22p63s1
Lewis Symbol

8. Cl Na Ne core implied in symbol 1s22s22p63s23p5 1s22s22p63s1
Lewis Symbol

9. IONIC BONDING  Cl Cl Na Na+
the formation of ionic bonds is represented
in terms of Lewis symbols Cl Cl Na 
Na+
1s22s22p63s23p6
1s22s22p6
the loss or gain of electrons(dots) until
both species have reached an octet of electrons

10. represents one orbitalCl Cl
[Ne] 3s23p6
represents one orbital
(Pauli: 2 electrons)

11. ions stack together in regular crystalline structures
electrostatic interaction
ionic solids typically
1. high melting and boiling points
2. brittle
3. form electrolyte solutions if they dissolve in water

12. Li(s) + ½ F2(g) → LiF(s) enthalpy of formation lattice energy
Li+(g) + F-(g) → LiF(s)
Hess’s Law
enthalpy is a state function
Born-Haber Cycle

13. Li(s) + ½ F2(g) → LiF(s) Li+(g) + F-(g) Li(g) + F(g) Li(s) + ½ F2(g)5
ΔHoR= Σ ΔHoi
i=1
ΔHo4
ΔHo3
ΔHo5
Li(g) + F(g)
ΔHo1
ΔHo2
ΔHoR
Li(s) + ½ F2(g)
LiF(s)

14. Mg(s) + ½ O2(g) → MgO(s) Mg2+(g) + O2-(g) Mg+(g) + O-(g) Mg(g) + O(g)
ΔHo6 7
ΔHo5
ΔHoR= Σ ΔHoi
i=1
Mg+(g) + O-(g)
ΔHo7
ΔHo3
ΔHo4
Mg(g) + O(g)
ΔHo1
ΔHo2
ΔHoR
MgO(s)
Mg(s) + ½ O2(g)

15. Lattice Energy of Ionic Compounds
SUMMARY
Lewis Dot
Octett Rule
Lattice Energy of Ionic Compounds
600 – 4000 kJmol-1

16. Homework
Chapter 9
pages , problem sets