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I II III IV
Chemical Bonding
I. Introduction toBonding
A. Vocabulary
Chemical Bond
attractive force between atoms or ions that binds them together as a unit
IONIC COVALENTBond Formation
Type of Structure
Solubility in Water
Electrical Conductivity
OtherProperties
e- are transferred from metal to nonmetal
high
yes (solution or liquid)
yes
e- are shared between two nonmetals
low
no
usually not
MeltingPoint
crystal lattice true molecules
B. Types of Bonds
Physical State solid liquid or gas
odorous
“electron sea”
METALLICBond Formation
Type of Structure
Solubility in Water
Electrical Conductivity
OtherProperties
MeltingPoint
B. Types of Bonds
Physical State
e- are delocalized among metal atoms
very high
yes (any form)
no
malleable, ductile, lustrous
solid
C. Bond Polarity
Difference in electronegativity determines bond type.
Above 1.7 = ionic
0.3-1.7 = polar covalent
0-0.3 = non-polar covalent
C. Bond Polarity
Electronegativity Attraction an atom has for a shared pair
of electrons. higher e-neg atom has a partial negative
charge -
lower e-neg atom has a
partial positive charge +
Nonpolar Covalent Bond e- are shared equally usually between identical atoms
• Ex. F2
C. Bond Polarity
+ -
C. Bond Polarity
Polar Covalent Bond e- are shared unequally results in partial charges (dipole)
Nonpolar
Polar
Ionic
View Bonding Animations.
C. Bond Polarity
C. Bond Polarity
Examples:
Cl2
HCl
NaCl
3.0-3.0=0.0Nonpolar
3.0-2.1=0.9Polar
3.0-0.9=2.1Ionic
D. Lewis Structures
Electron Dot Diagrams show valence e- as dots
EX: oxygen
2s 2pO
X
D. Lewis Structures
Covalent – show sharing of e-
Ionic – show transfer of e-
D. Lewis Structures
Covalent – show sharing of e-
Ionic – show transfer of e-
+ -
+
D. Lewis Structures
Nonpolar Covalent - no charges
Polar Covalent - partial charges
18Steps for Building a Dot Steps for Building a Dot StructureStructureSteps for Building a Dot Steps for Building a Dot StructureStructure
Ammonia, NHAmmonia, NH33
1. Decide on the central atom; never H. 1. Decide on the central atom; never H. Why?Why?
If there is a choice, the central atom is atom of If there is a choice, the central atom is atom of lowest affinity for electrons. lowest affinity for electrons. (Most of the time, this (Most of the time, this is the is the least electronegative .least electronegative .)Therefore, N is central Therefore, N is central on this oneon this one
2. Add up the number of valence electrons 2. Add up the number of valence electrons that can be used.that can be used.
H = 1 and N = 5H = 1 and N = 5
Total = (3 x 1) + 5 Total = (3 x 1) + 5
= 8 electrons / 4 pairs= 8 electrons / 4 pairs
19
3.3. Form a single bond Form a single bond between the central atom and between the central atom and each surrounding atom (each each surrounding atom (each bond takes 2 electrons!)bond takes 2 electrons!)
H H
H
N
Building a Dot StructureBuilding a Dot Structure
H••
H
H
N4.4. Remaining electrons form Remaining electrons form LONE PAIRS to complete the LONE PAIRS to complete the octet as needed (or duet in the octet as needed (or duet in the case of H).case of H).
3 BOND PAIRS and 1 LONE 3 BOND PAIRS and 1 LONE PAIR.PAIR. Note that N has a share in 4 pairs (8 Note that N has a share in 4 pairs (8
electrons), while H shares 1 pair.electrons), while H shares 1 pair.
20
5.5. Check to make sure there are 8 Check to make sure there are 8 electrons around each atom electrons around each atom except H. H should only have 2 except H. H should only have 2 electrons. This includes electrons. This includes SHARED pairs. SHARED pairs.
Building a Dot StructureBuilding a Dot Structure
6. 6. Also, check the number of electrons in Also, check the number of electrons in your drawing with the number of your drawing with the number of electrons from step 2. If you have more electrons from step 2. If you have more electrons in the drawing than in step 2, electrons in the drawing than in step 2, you must make double or triple bonds. If you must make double or triple bonds. If you have less electrons in the drawing you have less electrons in the drawing than in step 2, you made a mistake!than in step 2, you made a mistake!
H••
H
H
N
21
Carbon Dioxide, COCarbon Dioxide, CO22Carbon Dioxide, COCarbon Dioxide, CO22
1. Central atom = 1. Central atom =
2. Valence electrons =2. Valence electrons =
3. Form bonds.3. Form bonds.
O OC4. Place lone pairs on outer atoms.4. Place lone pairs on outer atoms.
This leaves 12 electrons (6 pair).This leaves 12 electrons (6 pair).
5. Check to see that all atoms have 8 electrons 5. Check to see that all atoms have 8 electrons around it except for H, which can have 2.around it except for H, which can have 2.
C 4 e-C 4 e-O 6 e- X 2 O’s = 12 e-O 6 e- X 2 O’s = 12 e-Total: 16 valence Total: 16 valence electronselectrons
22
Carbon Dioxide, COCarbon Dioxide, CO22Carbon Dioxide, COCarbon Dioxide, CO22
••O OC
•• ••
••••••
••O OC
•• ••
••••••
••O OC
•• ••
••
••O OC
•• ••
••
6. There are too many electrons in our drawing. 6. There are too many electrons in our drawing. We must form DOUBLE BONDS between C and O. We must form DOUBLE BONDS between C and O. Instead of sharing only 1 pair, a double bond Instead of sharing only 1 pair, a double bond shares 2 pairs. So one pair is taken away from shares 2 pairs. So one pair is taken away from each atom and replaced with another bond.each atom and replaced with another bond.
C 4 e-C 4 e-O 6 e- X 2 O’s = 12 e-O 6 e- X 2 O’s = 12 e-Total: 16 valence electronsTotal: 16 valence electrons
How many are in the drawing?How many are in the drawing?
23Double and Double and even triple even triple bonds are bonds are commonly commonly observed for observed for C, N, P, O, and C, N, P, O, and SS
••O OC
•• ••
••
••O OC
•• ••
••
HH22COCO
SOSO33
CC22FF44
24
Now You Try One!Now You Try One!Draw Sulfur Dioxide, SODraw Sulfur Dioxide, SO22
Now You Try One!Now You Try One!Draw Sulfur Dioxide, SODraw Sulfur Dioxide, SO22