Bonding & Naming
Honors Supplement
Bonding and Naming Honors Supplement
Lattice Energy
Definition:
lattice energy = energy released when a crystal containing 1 mole of an ionic compound is
formed from gaseous ions.
Related to charge on the ion and distance between nuclei
 higher charge  stronger pull
 smaller means closer together  stronger pull
Table 8-3 from your textbook: Lattice Energies of Some Ionic Compounds
Compound
Lattice Energy
Compound
Lattice Energy
(kJ/mol)
(kJ/mol)
KI
-632
KF
-808
KBr
-671
AgCl
-910
RbF
-774
NaF
-910
NaI
-682
LiF
-1030
NaBr
-732
SrCl2
-2142
NaCl
-769
MgO
-3795
Peruse this table –
What happens as the ionic radius increases? (e.g. Check out the Na compounds or the F
compounds)
What happens as the amount of charge on a single ion increases? Both ions? (look at
bottom right hand corner of table)
Predict whether the lattice energy of CsCl is larger or smaller than that of KCl.
Predict whether the lattice energy of Na2O will be larger of smaller than that of MgO.
What do you think will be the effect of lattice energy on melting point?
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Bonding & Naming
Honors Supplement
Oxidation Numbers
Oxidation number = the charge on an ion
e.g. K+ has an oxidation number of 1+
O2- has an oxidation number of 2We use oxidation numbers to figure out the formulas of ionic compounds.
The sum of oxidation numbers for the formulas of an ionic compounds must = 0.
Oxidation Numbers Practice Problems
The oxidation number of an atom is the apparent charge assigned to it in a particular molecule or ion. Certain rules are
followed in assigning oxidation numbers.
The oxidation number of:
 an element in the uncombined state is 0.
 a monatomic ion equals the charge on the ion.
 hydrogen is generally +1; in hydrides, -1.
 oxygen is generally -2; in peroxides, -1.
 the more electronegative element in a binary covalent compound is negative, while that of the other element is
positive.
 elements other than oxygen and hydrogen in a neutral compound is such that the sum of the oxidation numbers for
all atoms in the compound is 0.
 elements other than oxygen and hydrogen in a polyatomic ion is such that the sum of the oxidation numbers for all
atoms in the ion equals the charge on the ion.
Use these rules to assign oxidation numbers to each element in each of the given formulas.
e.g. H2O +1, -2
N2
0
1. Cl2
2. Cl3. Na
4. Na+
5. KCl
6. H2S
7. CaO
8. H2SO4
9. NO310. Cr2O7211. NH4Cl
12. NH3
13. NO2
14. CaH2 (calcium hydride)
15. Na2O2 (sodium peroxide)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Prentice Hall Inc.
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Bonding & Naming
Honors Supplement
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Bonding & Naming
Honors Supplement
Sigma Bonds and Pi Bonds
•
Sigma () bonds: electron density lies on the axis between the nuclei.
•
•
All single bonds are bonds.
What about overlap in multiple bonds?
• Pi () bonds: electron density lies above and below the plane of the nuclei.
• A double bond consists of one  bond and one  bond.
• A triple bond has one  bond and two  bonds (above and below the
plane of the nuclei; in front of and behind the plane of the nuclei).

Compare C2H6, C2H4, C2H2.
Formation of a Double Bond
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Double Bond (C2H4)
Triple Bond (C2H2)
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Bonding & Naming
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Naming Molecular Compounds
B. Stock system
oxidation numbers
Treat molecular compounds (esp. those with polar covalent bonds) as if they are ionic:
1.
Use electronegativities to determine which atom is more electronegative 
negative (-) oxidation number (usually = ionic charge)
2.
Assign positive oxidation number to other element.
Note: Sum of oxidation numbers in a neutral compound = 0.
Practice:
CCl4
CO
CO2
As2S3
P2O5
P4O10
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Bonding & Naming
Honors Supplement
Hybridization (Honors only)

Atomic orbitals are mixed  new, identical hybrid orbitals

Helps to explain VSEPR

# of hybrid orbitals = # atomic orbitals mixed, including lone pairs
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Honors Supplement
Hybrid Orbital Summary
Electron-domain geometry must be known before hybridization is assigned.
• To assign hybridization:
• Draw a Lewis structure.
• Assign the electron-domain geometry using VSEPR theory.
• Specify the hybridization required to accommodate the electron pairs based on
their geometric arrangement.
• Name the geometry by the positions of the atoms.
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