Chemical Bonding
Chapter 6
Pages 174-213
(no Section 4)
The breaking of bonds
and the forming of
bonds occur during
chemical reactions.
Aspirin
What is the
formula for a
molecule of
aspirin?
Is it an ionic or
covalent
(molecular)
compound?
What do we call the things that hold a
molecule of aspirin together?
• C9H8O4
• covalent compound (made of all nonmetals - no ions)
Aspirin
• C9H8O4
• covalent compound (made of all nonmetals - no ions)
Aspirin (Odyssey Program)
• C9H8O4
• covalent compound (made of all nonmetals - no ions)
The Attachment Between Atoms
atoms combine to form
ionic bonds
(M + NM)
covalent bonds
(NM + NM)
chemical bond – a mutual electrical
attraction between the nuclei and valence
electrons of two atoms that binds the
atoms together
Ionic Bonding
• ionic bond – electrical attraction between
cations and anions; when electrons are taken
by one atom from another atom
metal and a nonmetal
NaCl
cation and anion
(The charges are “hidden” to make a neutral compound.)
Ionic Bonding: taking of electrons
Na 11e-
F 9e-
Na+ 10e- STABLE!!!
F- 10e- STABLE!!!
3s
3s
2p
2p
2s
2s
1s
1s
I’m
Positive!
A metal ion
atom A nonmetal ion
atom
I’m
Negative
I’m
Positive!
A metal ion A nonmetal ion
I’m
Negative
When a metal and a nonmetal atom are
around each other there is the opportunity
for….
…the transfer of electrons producing ions
that would like to cling to each other.
Ionic bonding!!!
The simplest ratio of the packed
ions is called:
“cubic”
shape
The Formula Unit
Ex: NaCl
Ions
• Metals form cations.
(metals lose e )
• Nonmetals form anions.
(nonmetals gain e )
Ions
• cations (+)
• anions (-)
• monatomic ions – ions
• formed from one atom
Na+ or O-2
Examples:
• polyatomic ions - ions formed from two or
more atoms bonded together
Examples: NH4+ or SO4-2
Naming Ions
• monatomic ions
• cations – named like the atom, only add ion to it
» Example: Na+
is the sodium ion
• anions – remove the ending to the atom name and add
–ide and ion to it
» Example: Clis the chlorine
+ide ion
or the chloride ion
• polyatomic ions
• You do not determine their names, you memorize them
Ionic Compounds
• solid at room temperature (forming crystals)
• high melting points (thus are usually solid at RT)
• formula unit represents the lowest ratio of ions
that combine to form a neutral compound
• when dissolved in water, the ionic compounds
will break up into ions (dissociate)
• the solutions of ionic compounds will conduct
electricity (electrolytes)
Dissociation
NaCl(s) 
 Na (aq) + Cl (aq)
H2O(l)
solid
placed in water
+
-
hydrated ions
(surrounded by water)
dissociation – when an ionic compound dissolves
to break apart into hydrated ions
Dissociation
Electrolytes and Nonelectrolytes
When an ionic compound
dissolves to produce ions, it is
called an electrolyte because it
conducts electricity in water.
When an compound does not
dissolve to produce ions, it is
called a nonelectrolyte because
it does not conduct electricity in
water.
Electrolytes or salt?
Check for Understanding
1. What kinds of atoms form ionic bonds?
2. What is a polyatomic ion?
3. Name 5 things you learned about ionic
compounds.
You Try It.
Do the Dissociation Equations worksheet.
Covalent Bonding
covalent bond – when electrons are shared
between two atoms
– the electronegativity difference between the
two atoms is less than 1.7
– usually two nonmetals
– NO ions formed! (no electrons are taken…just
shared)
When a nonmetal and another
nonmetal atom are around
each other there is the
opportunity for….
…the sharing of electrons
producing molecules in which
the atoms like to cling to each
other.
Covalent bonding!!!
The formation of a bond
between two nonmetal atoms.
Atoms sufficiently far
apart to have no
interaction
Figure 5 Page 179
Covalent Compounds
•
•
•
•
Also called molecular compounds
solid, liquid, or gas at room temperature
low melting points
molecular formula represents the actual ratio of
atoms that combine to form a neutral compound
• when dissolved in water, the molecular
compounds DO NOT break up into ions
(NO dissociation)
• the solutions of molecular compounds DO NOT
conduct electricity (nonelectrolytes)
Pure
Covalent
The two
fundamental
types of bonds.
Ionic
There is
another type
of bond, not
purely
covalent
and not
purely ionic.
Nonpolar
Pure
Covalent
Polar
Covalent
Ionic
Sharing of Electrons
• How would you know if an electron is
going to be taken by one atom from
another?
• Is there ever a time in which the electron is
not taken but shared?
• Is the electron always shared equally?
Electronegativity
• electronegativity – a measure of the ability of
an atom in a chemical compound to attract
electrons from another atom in the
compound
The difference in electronegativity values for
two atoms will indicate whether the two
atoms form an ionic bond (e- taken) or a
polar or nonpolar covalent bond (e- shared).
Electronegativity Differences
•
•
•
0.0 to 0.4 nonpolar covalent
0.5 to 1.6 polar covalent
1.7 and up ionic
These ranges are flexible, although the
general rule is a metal and nonmetal will
form an ionic bond and two nonmetals will
form a covalent bond.
(Learn these values!)
PS: They are different than your book!
Ionic, Polar Covalent, or
Nonpolar Covalent?
What kind of bond would each pair form?
1. N and S
2. S and C
3. Mg and Cl
4. C and F
5. Ba and O
Which one of these bonds has the least
ionic character?
Valence Electrons
• valence electrons – the electrons in the
highest energy level
Na: 1s22s22p63s1 - 1 valence eO: ?
Ne: ?
Al: ?
He: ?
Octet Rule
• octet rule – most atoms will gain or lose
electrons to have 8 valence electrons (e- in
the highest energy level)
– Exceptions: H, He, Li, Be, B, and some atoms
P and higher on the periodic table
Why is an atom like Ca more stable
once it becomes an ion?
How many valence electrons would
calcium have to lose to have 8?
VSEPR Theory
Valence
Shell
Electron
Pair
Repulsion
Repulsion between the sets of
valence-level electrons
surrounding an atom causes
these sets to be oriented as far
apart as possible.
Theory
Regions of Electron Density
What is a Region of electron density?
• Single bond (2e- connecting 2 atoms)
• Double bond (4e- connecting 2 atoms)
• Triple bond (6e- connecting 2 atoms)
• Lone pair (unbonded pair) (2e- alone on an
atom)
LINEAR
180o
2 Regions of Electron Density
2 Bonds
bonded pair
of electrons
bonded pair
of electrons
TRIGONAL PLANAR
120o
3 Regions of Electron Density
3 Bonds
3 bonded pairs
of electrons
You don’t have to know this!
BENT
119o
3 Regions of Electron Density
2 Bonds & 1 Lone Pair
2 bonded pairs
of electrons
1 lone pair
of electrons
TETRAHEDRAL
109.5o
4 Regions of Electron Density
4 Bonds
4 bonded pairs
of electrons
TRIGONAL PYRAMIDAL
107o
4 Regions of Electron Density
3 Bonds & 1 Lone Pair
1 lone pair
of electrons
3 bonded pairs
of electrons
BENT
105o
4 Regions of Electron Density
2 Bonds & 2 Lone Pairs
All of these have 4 regions of
electron density
(although the number of bonded pairs is different)
TRIGONAL BIPYRAMIDAL
120o & 90o
5 Regions of Electron Density
5 Bonds
SEE-SAW
You don’t have to know this!
120o & 90o
5 Regions of Electron Density
4 Bonds & 1 Lone Pair
T-SHAPED You don’t have to know this!
120o & 90o
5 Regions of Electron Density
3 Bonds & 2 Lone Pairs
LINEAR
You don’t have to know this!
180o
5 Regions of Electron Density
2 Bonds & 3 Lone Pairs
OCTAHEDRAL
90o
6 Regions of Electron Density
6 Bonds
SF6
SQUARE PYRAMIDAL
approximately 90o
6 Regions of Electron Density
5 Bonds & 1 Lone Pair
BrF5
You don’t have to know this!
SQUARE PLANAR
90o
6 Regions of Electron Density
4 Bonds & 2 Lone Pairs
ICl4-