HC Bonding Lecture.notebook
October 21, 2011
O
O
H
C
C
H
H
Types of
Chemical Bonding
N
O
H
H
O
H
O
H
C
C
O
H
H
H
H
H
C
H
O
O
N
H
H
O
O
H
Sep 28­7:56 AM
What is a chemical bond???
• an attraction between atoms that lead to
the formation of chemical compounds
• the "attraction" involves the valence
electrons of the atoms
Different Types:
covalent
ionic
metallic
Sep 28­9:26 AM
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HC Bonding Lecture.notebook
October 21, 2011
Covalent Bonding...
• bonding between two or more non-metals
• involves a sharing of electrons between the two
atoms in the bond
• characteristics of covalent compounds:
low melting & boiling points (compared to ionic)
tend to be powders or in "softer" forms than ionic
more flammable than ionic compounds
do not easily dissolve in water
when dissolved, do not conduct electricity
Examples:
water (H2O)
propane (C3H8)
ammonia (NH3)
Sep 28­7:56 AM
Ionic Bonding...
• bonding between metals & non-metals
• involves a transfer of electrons from the metal(s)
(low electronegativity) to the non-metal(s) (high
electronegativity
• characteristics of ionic compounds:
all form crystals, are hard a brittle
have high melting and boiling points
more easily dissolvable in water than covalent
when dissolved, conduct electricity
Examples:
salt (NaCl)
sulfuric acid (H2SO4)
baking soda (NaHCO3)
Sep 28­7:56 AM
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HC Bonding Lecture.notebook
October 21, 2011
Third Type: Metallic Bonding...
• bonding between metals
• each metal atom gives up a valence electron to a
"sea" of electrons
• have high melting and boiling points
• form dense materials
• compounds are malleable
Examples: aluminum foil (Al)
tin foil (Sn)
iron (Fe)
Sep 28­8:20 AM
A Note About Hydrogen...
• can participate in both covalent & ionic
bonding
• when listed 1st, compound is ionic; HCl
• when listed 2nd or later, compound is
covalent; CH4
• exception: water: H2O - always covalent
Sep 28­9:26 AM
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HC Bonding Lecture.notebook
October 21, 2011
Naming Covalent Compounds
use prefixes listed on the back of periodic table,
mono, di, tri, etc..., to indicate number of each
atom in compound
prefix "mono" is optional for 1st element,
required for 2nd element
change the ending of the 2nd element to "-ide"
Examples:
SF6
iodine tribromide
C3H8
diphosphorus tetraoxide
NO
carbon tetrafluoride
Sep 28­9:34 AM
Lewis Structures
Diagrams that show the bonding
between atoms in a covalent
compound.
Sep 23­12:39 PM
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HC Bonding Lecture.notebook
October 21, 2011
Lewis Dot Structures for Atoms
H
Be
B
C
N
O
F
Ne
# valence e-
1
2
3
4
5
6
7
8
# bonds
1
2
3
4
3
2
1
0
linear
trigonal
tetra-
trigonal
planar
hedral
pyramid
120o
109.5o
107.3o
linear
shapes
bond angles
180o
180o
bent
linear
98o
180o
Other Shapes...these break the octet rule
Octahedral: 6 atoms bonded to central atom
SF6
Trigonal Bipyramid: 5 atoms bonded to central atom
PCl5
Oct 4­9:36 AM
Guidelines...
Octet Rule: All atoms must have 8
electrons around them (a "stable octet")
• Exceptions to the octet rule:
H - only 1 bond, no dots
Be - 2 bonds, no dots
B - 3 bonds, no dots
• total up the valence electrons
• central atom = atom with least # of valence
electrons (never hydrogen)
• If more than one central atom string them
together first.
• Bond all other atoms to the central atom or atoms
making the structure as symmetrical as possible.
• Fill in the octets with pairs of dots.
• NO BOXES!!! DO NOT STRING OXYGENS!!!
Sep 23­12:41 PM
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HC Bonding Lecture.notebook
October 21, 2011
H2 O
CF4
F2
NCl3
C2H4F2
N2 I 4
Oct 4­9:52 AM
Double & Triple Bonds
Sometimes the electron count doesn't match up
with a single bonded structure.
Example:
N2
O2
C2H4
CF2O
NO BOXES!!!!
DO NOT STRING OXYGENS!!!
SO3
S
O
Not correct!!!!
O O
Oct 5­7:57 AM
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HC Bonding Lecture.notebook
October 21, 2011
Lewis Structures of Ions
• When counting the valence electrons, add (- ion) or subtract (+ ion)
the appropriate number of electrons according to the charge.
• Add brackets around the Lewis structure and indicate the charge of
the ion outside.
Example:
CO3-2
Oct 5­9:49 AM
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