13 December 2011
Objective: You will be able to:
 describe the three types of bonding and
determine which type of bonding is
present in a compound
 Do now: On the first slide of your
handout, brainstorm everything you know
about bonding.
 Homework: p. 400 #5, 6, 16, 17, 20, 21
due tomorrow, will be checked

Agenda
I.
II.
Do now
Ionic vs. Covalent vs. Metallic Bonding
Notes, Videos and Demo
Chemical Bonding

What do you know about bonding?

chemical bond: a strong force of
attraction that holds two atoms together.
Involves only the valence electrons.
Types of Bonds






ionic: attractive force between ions of
opposite charges, often a metal cation and a
non-metal anion.
covalent: results from sharing electrons
between two atoms, usually non-metal atoms.
http://www.youtube.com/watch?v=QqjcCvzWwww
http://www.youtube.com/watch?v=yjge1WdCFPs
metallic: occurs when the nuclei of a
collection of metal atoms simultaneously
attract their collective electrons.
http://www.drkstreet.com/resources/metallic-bonding-animation.swf
Ionic or Covalent?
Why? Which have both ionic and covalent
bonds?
a. KBr
b. SO2
c. H2SO4
d. CH3COOH
e. Na3PO4
f.
CaCO3

Lewis symbol
valance electrons as dots
 Draw the Lewis symbol of the first 18
elements.
 left, right, top, bottom, top, bottom left,
right

octet rule: representative elements tend
to gain, lose, or share electrons until they
are surrounded by eight valence electrons
(an octet)
 This gives atoms noble gas configuration
with full s and p sublevels
 Noble gas configurations are very stable.
 Hydrogen requires only two electrons to
attain noble gas configuration

14 December 2011
Objective: You will be able to:
 describe ionic and covalent bonding and
draw Lewis structures for covalent
compounds.
 Homework Quiz: Week of Dec. 12
a. Draw dot diagrams for sodium and sulfur.
b. Using arrows, show what happens to their
valence electrons when they bond.
c. Write the name of the compound formed.

Agenda
Homework Quiz
 Homework answers
 Isoelectronic ions
 Ionic bonding and lattice energy
 Covalent Bonding
 Lewis Structures
Homework: p. 401 #30, 35, 39, 41, 44

Isoelectronic
having the same electron configuration as
a noble gas
 When an element attains a noble gas
configuration, does it turn into a noble
gas? Why or why not?
 Which are isoelectronic with one another?
 N3-, K+, Ca2+, O2-, F-, Ne, Br-, Kr, Sc3+,
Na+, Al3+, Se2-, Mg2+

Ionic Bonding




Ions form when electrons transfer from an
atom of low ionization energy (usually a
metal) to an atom of high electron affinity
(usually a non-metal).
The electrostatic attraction between two
oppositely charged ions = ionic bond
Crystal lattice demo
http://www.mhhe.com/physsci/chemistry/ani
mations/chang_7e_esp/bom1s2_11.swf
lattice: a stable, ordered, solid, 3D array of
ions.
 lattice energy, ∆Hlattice, is the energy
required to completely separate a mole of
solid ionic compound into its gaseous ions.
KF(s) → K+(g) + F-(g) ∆Hlattice = +808 kJ/mol

Example Lattice Energies
Compound
LiF
LiCl
LiI
NaF
NaCl
NaBr
NaI
Lattice Energy (kJ/mol)
1030
834
730
910
788
732
682
Ions of Transition Metals
Remember that the d orbital fills before s
 When a transition metal is ionized, it loses
the s electrons before the d electrons
 Fe
[Ar] 3d6 4s2
 Fe2+ [Ar] 3d6
 Fe3+ [Ar] 3d5
3+
 Write the electron configuration for Cr
and Sn4+

Covalent Bonding
formed between two atoms that share one
or more pairs of electrons
 Lewis structures show shared pairs of
electrons (bonding pairs)
 carbon dioxide:

Lewis Structures
Rules
1.
Total the valance electrons of all the bonded
atoms
2. Use one pair of electrons to bond each outer
atom to the central atom (usually the atom in
least abundance)
3. Complete the octets around the outer atoms
4. Place any remaining electrons on the central
atom
5. If there are not enough electrons to give the
central atom an octet, make multiple bonds.
NO3-
Practice Problems
Br2
 CH4
 H2O
 H2CO
 SeF2
 CF4

CHCl3
 CO2
 BF3
 SO3
 NH4+
 HCN

Resonance Structures
two or more Lewis structures that are
equally good representations of the
bonding in a molecule or ion.
 Usually differ only in the positions of
multiple or single bonds and unpaired
electrons

Formal Charge
the number of valence electrons in an
isolated atom minus the number of
electrons assigned to the atom in the
Lewis structure
 Used to determine which Lewis structure
is the most suitable to represent bonding
 Choose the one closest to zero.

Steps to Formal Charge
Examine each atom one at a time.
2. Count both electrons in a lone pair
(nonbonding electrons) and one electron
per bond.
3. Compare this number with the group
number.
4. If you have one less electron than the
group # indicates, the charge is +1
One more electron than the group #, the
charge is -1, etc.
1.
Example: Nitrate Ion
Example: Ammonium Ion
Formal Charge Practice Problems
a.
b.
c.
ClO3CHO2C2H3Cl
19 December 2011
Objective: You will be able to:
 calculate bond energies and review
chemical bonding
 Homework Quiz: Draw two resonance
structures for diazomethane, CH2N2. Show
formal charges for both structures. The
skeletal structure is:
H
C N N
H

Agenda
Homework Quiz
II. Bond strength and enthalpy
III. Problem Set
Homework: Problem Set due Weds.
I.
Strengths of Covalent Bonds




∆HBDE = bond dissociation energy (bond
enthalpy)
the enthalpy change for the breaking of
bonds in one mole of a gaseous substance
Bond breaking ∆H always positive,
always endothermic
Bond making is exothermic!
∆Hrxn = sum of the bond enthalpies of the
broken bonds – sum of the bond
enthalpies of the bonds formed
 Multiple bonds are shorter and stronger
than single bonds

Example

Use average bond enthalpies to estimate
the enthalpy change of the following
reaction:
2H2O → 2H2 + O2
Practice Problems
Calculate the enthalpy of reaction for the
process:
a. H2(g) + Cl2(g) → 2HCl(g)
b. H2(g) + F2(g) → 2HF(g)
c. H2(g) + C2H4(g) → C2H6(g)

This week…
Today: Problem Set Work Time
 Tomorrow: Green crystal lab part 1:
reaction and growing crystals
 Thurs: Green crystal lab parts 2 and 3:
Washing and drying crystals
 and problem set work time
 Problem set due Tuesday after vacation
 Vacation Assignment (distributed
tomorrow) due Wednesday after vacation

21 December 2011
Objective: You will be able to:
 synthesize a green crystal for later
analysis
 Do now:
 Grab a pair of goggles and sit with your
lab partner.
 Take out the lab packet.

Reaction and reagents





iron (III) chloride hexahydrate with potassium
oxalate
iron (III) chloride is a brown solution at the
front lab tables
 pipette 8 mL
potassium oxalate is a white crystal at the side
lab tables
 weigh 12 grams on weighing paper
distilled water is in the wash bottles
ice is in the white coolers at the front – you
can put your product beaker directly into the
cooler
Work quickly
Your product needs to chill for about 30
minutes before you pour off the solvent
and redissolve your crystals!
 We’ll store the crystals in a sample bottle
tomorrow.
 Work on your problem set while you wait.
 For now, collect data on your lab handout.

22 December 2011

Objective: You will be able to:
 separate your crystal from the solution
and dry it
Winter Break Assignment
Liquids and Intermolecular Forces
 Read pages 461-472 and 489-499
 Complete the following problems by
Tuesday, Jan. 3:
 page 504 #1, 2, 5, 6, 7, 10, 12, 14, 16, 18,
21, 22, 24, 25, 59, 60, 62, 66, 70, 72, 73,
79, 81, 85, 91, 94

Today
Watch demo of vacuum filtration.
 Complete Day 2 and Day 3 of experiment
 Work on problem set in pairs
 work efficiently and quietly
 stay in your seat unless you need to
move around for the lab
