Chemical Bonding
The keys to chemistry!
1
Bonding
3 types:
1.Ionic bonding
e.g. Table Salt (NaCl)
2. Covalent bonding
e.g. Water (H2O)
3. Metallic bonding
e.g. Iron
2
Chapter 15 Looks at:
Ionic bonding:
Valence electrons are
transferred between atoms
Metallic bonding:
Valence electrons are
mobile within the metal
3
Valence Electrons
Can be determine from the
electron configuration.
Na 2-8-1  1 valence
e
S
e
2-8-6  6 valence
4
Lewis Dot Symbols
(shows number of valence
Na
N
F
S
e)
5
Lewis Dot Symbols
You Try It !!!
Write the dot structures for:
Al
Ca
C
Ne
6
Def: Ionic Bond:
The “electrostatic” attraction
between a cation (+) and an
anion (-).
+
NaCl
Cation
+1 charge
+
-
-
Anion
-1 charge
(charges not written)
7
Ionic Compounds: Review
“Formula Unit”: the lowest ratio
of atoms in an ionic compound.
Formula unit
is NaCl
8
Ionic Formulas
•Calcium bromide
2+
Ca
Br
CaBr2 (balance charge)
•Copper(I) sulfate
+
Cu
SO4
Cu2SO4
29
Ionic Compounds: Try It
calcium nitrate
ammonium bromide
magnesium phosphate
calcium chromate
10
The Octet Rule
When forming compounds,
many atoms attain the electron
configuration of a noble gas
(8 valence electrons).
Ne
(exception is He with
2 valence electrons)
11
Cations
Metals tend to lose valence
electrons to achieve an octet.
Na
+
Na + 1e-
[Ne]
Ca
Ca2+ + 2e[Ar]
12
Atomic War!!
13
Cations
Transition metals are
more complicated.
-1e-
Cu
10
1
[Ar]3d 4s
+1
Cu
10
[Ar]3d
“pseudo noble gas”
e- configuration
14
Anions
Many nonmetals gain electrons
to achieve an octet.
F
+
e
F
-
[Ne]
O +
2e
O
215
Cations & Anions
Try It !!!
Write the dot structure for:
nitrogen atom
nitride ion
chlorine atom
chloride ion
magnesium atom
magnesium ion
16
Ionic Compounds
When Li and F react, an e- is
lost by Li and gained by F.
Li + F
+
Li
F
-
[He] [Ne]
17
Ionic Compounds: AlBr3
Recall for ionic compounds,
total charge must be zero.
Dot formula for
Br
a compound
+3
Al
Br
Br
Al 3 Br
[Ne]
[Kr]
18
Ionic Compounds
Write dot structures for
reactions of these atoms:
 Cs + F 
K+O
(total number of dots
stays the same)
19
Properties of
Ionic Compounds
(Strong electrostatic forces
hold ions in place.)
•solid at room temperature
•high MP
•conduct electrical current when
molten or in water (DEMO)
“electrolyte”
20
Electrical Conductivity
NaCl(s)
H2O
+
Na (aq)
+
Cl (aq)
mobile ions
Conduct electricity:
• charged particle
• free to move
21
The Metallic Bond
What holds metal
atoms together?
What gives metals
their special
properties?
22
The Metallic Bond
Regularly spaced cations in a
“sea” of valence electrons
+-
e
e
e
+- ++- +- e +- e + e +
e + e + e + e- + e
e
e
e
+
e
e
e
+
Na
valence
e
23
Def: Metallic Bond:
Attraction between fixed
metal cations and mobile
valence electrons.
explains
•electrically conductive
•heat conductive
•malleable
•ductile
24
Metals
High density because of
“close-packed” cubic or
hexagonal crystal structures.
25
Alloy
 a solid solution of
two or more metals.
Sterling silver: 93%Ag, 7%Cu
Stainless steel:
81%Fe, 18%Cr, .4%C, 1%Ni
What is:
bronze ?
14 carat gold ?
26
Don’t move or I’ll fill you full of
98% Pb, 1.0% Sb & 0.75 %Ag
What’s the
name of that
alloy?
A bullet !
Chemists in the Wild West
27
28
Warm-up
Write the formula for
tin(II) phosphate.
Write the e- dot symbol for:
Al, S, Ag, I
Define “ionic bond”.
29
Warm-up
What is the “octet rule?”
Write the e- dot symbol for:
•barium
•iodine
•barium iodide
30