Drill:
Ionic bonding
Objective:
Swbat: Demonstrate sharing of electrons in
order to model covalent bonding by combining
Lewis dot diagrams.
SAT ENRICHMENT:
The bonds in BaO are best described
as….
a.
b.
c.
d.
e.
Covalent, because valence electrons are shared.
Covalent, because valence electrons are transferred.
Ionic, because valence electrons are shared.
Ionic, because valence electrons are transferred.
Metallic, because valence electrons exist in a “mobile
sea”.
ENGAGEMENT:
Safari Montage Video: Properties of
Compounds: Covalent Bonding:
http://10.4.1.240/?p=d9e9fc51-8f49-11df8b67-002219bf32de
Covalent Bonding WebQuest!
Covalent Bonding Webquest
(SR.CHEMBOND.02A)
http://www.visionlearning.com/library/mod
ule_viewer.php?mid=55&mcid=&l=
Covalent Compounds
 Covalent Bonds
 Two nonmetals
 Weaker than ionic bonds
 Electrons shared, not transferred
Covalent Compounds
 Example: Chlorine and fluorine (ClF)
•••
• Cl
• •• +
◙◙
◙
F
◙◙
◙
◙
◙◙
•
•
→ •• Cl •◙ F ◙◙
•• ◙◙
 Problem 1: Sulfur and oxygen (SO)
• •S• • +
• •
◙
◙
O
◙◙
◙
◙
•••◙
•
→ • S • ◙ O ◙◙
◙◙
Covalent Compounds
 Problem 2: Selenium and bromine (SeBr2)
• Br• • +
•
•
••
◙
◙
◙◙
•••
•••
◙
◙
Se + • Br • → ◙ Se • Br •
◙
◙•
••
• Br
• ••
•
•
••
◙◙
◙
 Problem 3: Carbon and oxygen (CO)
•
•C• +
•
◙
◙
◙◙
◙◙
◙
•
•
→
O
C
◙◙ O ◙
•
•
◙
◙
Bond Polarity
If there is an unequal sharing of electrons, the
bonding electrons spend more time near the
atom with the highest electronegativity causing it
to obtain a slightly negative charge.
The atom with the lower electronegativity acquires
a slightly positive charge.
Electronegativities
 Electronegativities for the first six periods
The difference between two elements’ electronegativities
indicates the degree of electron sharing (or transfer) in a
chemical bond
The closer the electronegativity, the more equally the
electrons are shared.
H
2.1
Li
1.0
Be
1.5
B
2.0
C
2.5
N
3.0
O
3.5
F
4.0
Na
0.9
Mg
1.2
Al
1.5
Si
1.8
P
2.1
S
2.5
Cl
3.0
K
0.8
Ca
1.0
Sc
1.3
Ti
1.5
V
1.6
Cr
1.6
Mn
1.5
Fe
1.8
Co
1.9
Ni
1.9
Cu
1.9
Zn
1.6
Ga
1.6
Ge
1.8
As
2.0
Se
2.4
Br
2.8
Rb
0.8
Sr
1.0
Y
1.2
Zr
1.4
Nb
1.6
Mo
1.8
Tc
1.9
Ru
2.2
Rh
2.2
Pd
2.2
Ag
1.9
Cd
1.7
In
1.7
Sn
1.8
Sb
1.9
Te
2.1
I
2.5
Cs
0.7
Ba
0.9
La
1.0
Hf
1.3
Ta
1.5
W
1.7
Re
1.9
Os
2.2
Ir
2.2
Pt
2.2
Au
2.4
Hg
1.9
Tl
1.8
Pb
1.9
Bi
1.9
Po
2.0
At
2.2
Polar or Nonpolar?
Nonpolar Covalent BondElectronegativity difference ≤ 0.4
Polar Covalent Bond
0.4 < Electronegativity difference < 1.7
Predicting Bond Type
Example 1: OF2
EN of O = 3.5
EN of F = 4.0
4.0 – 3.5 = 0.5
0.5 is less than 1.7 but greater
than 0.4, so the bond is polar
covalent.
Predicting Bond Type
Example 2: Cl2
EN of Cl = 3.0
3.0 – 3.0 = 0.0
0 ≤ 0.4, so the bond is
nonpolar covalent.
Predicting Bond Type
Example 3: CS2
C: 2.5
2.5 – 2.5 = 0.0
S: 2.5
Nonpolar
Covalent
Predicting Bond Type
Example 4: NH3
N: 3.0
3.0 – 2.1 = 0.9
H: 2.1
Polar Covalent
Special Case: Polar Covalent
 Polar covalent molecules
have a dipole
 Molecules with dipoles have
partially charged ends
 For water:
•
•
Oxygen has an electronegativity of
3.5
Hydrogen has an electronegativity of
2.1
 Because oxygen is more
electronegative, it will be the
negative end of the dipole
 Because hydrogen is less
electronegative, it will be the
positive end of the dipole
Negative
◙
◙
◙◙
O ◙• H
◙•
H
Positive
Bonding
Complete bonding worksheet
Summary:
Did we accomplish the objective?
Explain.
Define a Covalent bond.
What criteria would you use to assess
whether a bond is ionic or covalent?
What criteria would you use to assess
whether a bond is polar or nonpolar?
Homework:
Chromatography Pre-Lab
(NO HOMEWORK PASSES MAY BE USED)
Drill:
Quiz: Covalent Bonding (5 min)
Objective:
Swbat: Demonstrate sharing of electrons in
order to model covalent bonding by combining
Lewis dot diagrams.
SAT ENRICHMENT:
Generally… valence electrons are needed
for atoms to be most stable.
a. 2
b. 6
c. 8
d. 18
e. 32
Chromatography Lab
Review Lab procedures.
Chromatography Lab
Exit Ticket & Extension
Covalent Bonding Exit ticket
Extension: Oil and Soap Molecule
Simulation: http://intro.bio.umb.edu/111112/111F98Lect/soapandoil.html
Summary
Did we accomplish the objective?
Explain.
Identify the purpose of the
chromatography lab.
Explain your chromatography lab
results. Which colors were soluble in
water?
Homework
Instructional Fair Pages 38 and 39!