“Ionic, Covalent and
Metallic Bonding”
modified from
Stephen L. Cotton
Valence Electrons are…?
in the outer energy level.
 Responsible for properties of
elements
 Valence electrons - The s and p
electrons in the highest occupied
energy level
 Core electrons – are those in the
energy levels below.
 electrons
Keeping Track of Electrons



Atoms in the same column...
1) Have the same outer electron
configuration.
2) Have the same valence electrons.
The number of valence electrons are
easily determined. It is the group
number for a representative element
Group 2A: Be, Mg, Ca, etc.
– have 2 valence electrons
Electron Dot diagrams are…





A way of showing & keeping
track of valence electrons.
How to write them?
Write the symbol - it
represents the nucleus and
inner (core) electrons
Put one dot for each valence
electron (8 maximum)
They don’t pair up until they
have to (Hund’s rule)
X
The Electron Dot diagram for
Nitrogen
Nitrogen has 5 valence
electrons to show.
 First we write the symbol.
Then add 1 electron at a
time to each side.
Now they are forced to pair up.
We have now written the electron dot
diagram for Nitrogen.

N
The Octet Rule

The Octet Rule: in forming compounds,
atoms tend to achieve a noble gas
configuration; 8 in the outer level is stable
 Each noble gas (except He, which has
2) has 8 electrons in the outer level
Formation of Cations
 Metals
lose electrons to attain a noble
gas configuration.
 They make positive ions (cations)
 If we look at the electron configuration,
it makes sense to lose electrons:
 Na 1s22s22p63s1 1 valence electron
 Na1+ 1s22s22p6 This is a noble gas
configuration with 8 electrons in the
outer level.
Electron Dots For Cations

Metals will have few valence electrons
(usually 3 or less); calcium has only 2
valence electrons
Ca
Electron Dots For Cations
Metals will have few valence electrons
 Metals will lose the valence electrons

Ca
Electron Dots For Cations
Metals will have few valence electrons
 Metals will lose the valence electrons
 Forming positive ions

2+
Ca
This is named the
“calcium ion”.
NO DOTS are now shown for the cation.
Electron Dots For Cations
 Let’s do Scandium, #21
 The electron configuration is:
2
2
6
2
6
2
1
1s 2s 2p 3s 3p 4s 3d
 Thus, it can lose 2e (making it
2+), or lose 3e (making 3+)
Sc =
2+
Sc
Scandium (II) ion
Sc =
3+
Sc
Scandium (III) ion
Electron Dots For Cations
Let’s
do Silver, element #47
Predicted configuration is:
1s22s22p63s23p64s23d104p65s24d9
Actual
configuration is:
1s22s22p63s23p64s23d104p65s14d10
Ag = Ag1+
(can’t lose any more,
charges of 3+ or greater are uncommon)
Electron Dots For Cations
 Silver did the best job it
could, but it did not achieve a
true Noble Gas configuration
 Instead, it is called a
“pseudo-noble gas
configuration”
Electron Configurations: Anions
 Nonmetals
gain electrons to attain
noble gas configuration.
 They make negative ions (anions)
 S = 1s22s22p63s23p4 = 6 valence
electrons
 S2- = 1s22s22p63s23p6 = noble gas
configuration.
 Halide ions are ions from chlorine or
other halogens that gain electrons
Electron Dots For Anions
Nonmetals will have many valence
electrons (usually 5 or more)
 They will gain electrons to fill outer shell.

P
3(This is called the “phosphide
ion”, and should show dots)
Bonds are…
 Forces that hold groups of
atoms together and make them
function as a unit. Two types:
bonds – transfer of
electrons (gained or lost; makes formula unit)
2) Covalent bonds – sharing of
electrons. The resulting
particle is called a “molecule”
1) Ionic
16
Covalent Bonds
 The
word covalent is a
combination of the prefix co(from Latin com, meaning “with”
or “together”), and the verb
valere, meaning “to be strong”.
 Two electrons shared together
have the strength to hold two
atoms together in a bond.
17
Molecules
 Many elements found in nature
are in the form of molecules:
 a neutral group of atoms joined
together by covalent bonds.
 For example, air contains oxygen
molecules, consisting of two
oxygen atoms joined covalently
 Called a “diatomic molecule” (O2)
18
How does H2 form?
(diatomic hydrogen molecule)
 The
nuclei repel each other,
since they both have a positive
charge (like charges repel).
+
+
+
19
+
How does H2 form?
 But,
the nuclei are attracted to
the electrons
 They share the electrons, and
this is called a “covalent bond”,
and involves only NONMETALS!
+
20
+
Covalent bonds
 Nonmetals hold on to their valence
electrons.
 They can’t give away electrons to bond.
– But still want noble gas configuration.
 Get it by sharing valence electrons with
each other = covalent bonding

21
By sharing, both atoms get to count
the electrons toward a noble gas
configuration.
Covalent bonding
 Fluorine
has seven valence
electrons (but would like to have 8)
F
22
Covalent bonding
 Fluorine
has seven valence
electrons
 A second atom also has seven
F
23
F
Covalent bonding
 Fluorine
has seven valence
electrons
 A second atom also has seven
 By sharing electrons…
F
24
F
Covalent bonding
 Fluorine
has seven valence
electrons
 A second atom also has seven
 By sharing electrons…
F
25
F
Covalent bonding
 Fluorine
has seven valence
electrons
 A second atom also has seven
 By sharing electrons…
F F
26
Covalent bonding
 Fluorine
has seven valence
electrons
 A second atom also has seven
 By sharing electrons…
F F
27
Covalent bonding
 Fluorine
has seven valence
electrons
 A second atom also has seven
 By sharing electrons…
F F
28
Covalent bonding
Fluorine has seven valence electrons
 A second atom also has seven
 By sharing electrons…

 …both
end with full orbitals
F F
29
Covalent bonding
Fluorine has seven valence electrons
 A second atom also has seven
 By sharing electrons…
 …both end with full orbitals

F F
30
8 Valence
electrons
Covalent bonding
Fluorine has seven valence electrons
 A second atom also has seven
 By sharing electrons…
 …both end with full orbitals

8 Valence
electrons
31
F F
32
Molecular Compounds
 The
formula for water is written as
H2O
–The subscript “2” behind hydrogen
means there are 2 atoms of
hydrogen; if there is only one atom,
the subscript 1 is omitted
 Molecular formulas do not tell any
information about the structure (the
arrangement of the various atoms).
33
- Page 215
These are some of the
different ways to represent
ammonia:
1. The molecular
formula shows
how many atoms
of each element
are present
2. The structural
formula ALSO
shows the
arrangement of
these atoms!
34
3. The ball and stick model is
the BEST, because it shows
a 3-dimensional arrangement.
A Single Covalent Bond is...
A
sharing of two valence electrons.
 Only nonmetals and hydrogen.
 Different from an ionic bond
because they actually form
molecules.
 Two specific atoms are joined.
 In an ionic solid, you can’t tell which
atom the electrons moved from or to
35
Water
Each hydrogen has 1 valence
electron
- Each hydrogen wants 1
more
 The oxygen has 6 valence
electrons
- The oxygen wants 2 more
 They share to make each
other complete

H
O
36
Water
 Put
the pieces together
 The first hydrogen is happy
 The oxygen still needs one more
HO
37
Water
 So,
a second hydrogen attaches
 Every atom has full energy levels
HO
H
38
Note the two
“unshared” pairs
of electrons
Multiple Bonds
 Sometimes
atoms share more than
one pair of valence electrons.
 A double bond is when atoms share
two pairs of electrons (4 total)
 A triple bond is when atoms share
three pairs of electrons (6 total)
 Table 8.1, p.222 - Know these 7
elements as diatomic:
What’s the deal
with the oxygen
Br2 I2 N2 Cl2 H2 O2 F2 dot diagram?
39
Dot diagram for Carbon dioxide
 CO2
C
O
40
- Carbon is central
atom ( more metallic )
 Carbon has 4 valence
electrons
 Wants 4 more
 Oxygen has 6 valence
electrons
 Wants 2 more
Carbon dioxide
 Attaching
1 oxygen leaves the
oxygen 1 short, and the carbon 3
short
CO
41
Carbon dioxide
 Attaching
the second oxygen
leaves both of the oxygen 1 short,
and the carbon 2 short
OC O
42
Carbon dioxide
 The
only solution is to share more
O CO
43
Carbon dioxide
 The
only solution is to share more
O CO
44
Carbon dioxide
 The
only solution is to share more
O CO
45
Carbon dioxide
 The
only solution is to share more
O C O
46
Carbon dioxide
 The
only solution is to share more
O C O
47
Carbon dioxide
 The
only solution is to share more
O C O
48
Carbon dioxide
 The
only solution is to share more
 Requires two double bonds
 Each atom can count all the
electrons in the bond
O C O
49
Carbon dioxide
The only solution is to share more
 Requires two double bonds
 Each atom can count all the electrons in
the bond
8 valence
electrons

O C O
50
Carbon dioxide
The only solution is to share more
 Requires two double bonds
 Each atom can count all the electrons in
the bond
8 valence
electrons

O C O
51
Carbon dioxide
The only solution is to share more
 Requires two double bonds
 Each atom can count all the electrons in
the bond
8 valence
electrons

O C O
52
HCN
 Put
single bond between each atom
 Need to add 2 more bonds
 Must go between C and N (Hydrogen is full)
HC N
53
HCN
Put in single bonds
 Needs 2 more bonds
 Must go between C and N, not the H
 Uses 8 electrons – need 2 more to
equal the 10 it has

HC N
54
HCN
Put in single bonds
 Need 2 more bonds
 Must go between C and N
 Uses 8 electrons - 2 more to add
 Must go on the N to fill its octet

HC N
55
A Coordinate Covalent Bond...
 When
one atom donates both
electrons in a covalent bond.
 Carbon monoxide (CO) is a good
example:
Both the carbon
and oxygen give
another single
electron to share
56
CO
Coordinate Covalent Bond
 When
one atom donates both
electrons in a covalent bond.
 Carbon monoxide (CO) is a good
example:
Oxygen
This carbon
electron
moves to
make a pair
with the other
single.
57
C O
gives both of
these
electrons,
since it has
no more
singles to
share.
Coordinate Covalent Bond
 When
one atom donates both
electrons in a covalent bond.
 Carbon monoxide (CO)
The
coordinate
covalent bond
is shown with
an arrow as:
C
58
O
C O
Resonance is...
 When
more than one valid dot
diagram is possible.
 Consider the two ways to draw ozone
(O3)
 Which one is it? Does it go back and
forth?
 It is a hybrid of both, like a mule; and
shown by a double-headed arrow
 found in double-bond structures!
59
Resonance in Ozone
Note the different location of the double bond
Neither structure is correct, it is
actually a hybrid of the two. To show
it, draw all varieties possible, and join
them with a double-headed arrow.
60
Resonance
Occurs when more than one valid Lewis
structure can be written for a particular
molecule (due to position of double bond)
•These are resonance structures of benzene.
•The actual structure is an average (or hybrid)
of these structures.
61
Polyatomic ions – note the different
positions of the double bond.
Resonance
in a
carbonate
ion (CO32-):
Resonance
in an
acetate ion
(C2H3O21-):
62
Ionic Bonding
 Anions
and cations are held together
by opposite charges (+ and -)
compounds are called salts.
 Simplest ratio of elements in an ionic
compound is called the formula unit.
 The bond is formed through the
transfer of electrons (lose and gain)
 Electrons are transferred to achieve
noble gas configuration.
 Ionic
Ionic Compounds
1)Also called SALTS
2)Made from: a CATION
with an ANION (or
literally from a metal
combining with a
nonmetal)
Ionic Bonding
Na Cl
The metal (sodium) tends to lose its one
electron from the outer level.
The nonmetal (chlorine) needs to gain one
more to fill its outer level, and will accept the
one electron that sodium is going to lose.
Ionic Bonding
+
Na
Cl
-
Note: Remember that NO DOTS
are now shown for the cation!
Ionic Bonding
Lets do an example by combining
calcium and phosphorus:
Ca

P
All the electrons must be accounted for,
and each atom will have a noble gas
configuration (which is stable).
Ionic Bonding
Ca
P
Ionic Bonding
2+
Ca
P
Ionic Bonding
2+
Ca
Ca
P
Ionic Bonding
2+
Ca
Ca
P
3-
Ionic Bonding
2+
Ca
P
Ca
P
3-
Ionic Bonding
2+
Ca
P
2+
Ca
P
3-
Ionic Bonding
Ca
2+
Ca
P
2+
Ca
P
3-
Ionic Bonding
Ca
2+
Ca
P
2+
Ca
P
3-
Ionic Bonding
2+
Ca
2+
Ca
2+
Ca
P
P
33-
Ionic Bonding
= Ca3P2
Formula Unit
This is a chemical formula, which
shows the kinds and numbers of atoms in
the smallest representative particle of the
substance.
For an ionic compound, the smallest
representative particle is called a:
Formula Unit
Properties of Ionic Compounds
1. Crystalline solids - a regular repeating
arrangement of ions in the solid: Fig.
7.9, page 197
– Ions are strongly bonded together.
– Structure is rigid.
2. High melting points
 Coordination number- number of ions
of opposite charge surrounding it
- Page 198
Coordination Numbers:
NaCl
Both the sodium
and chlorine have 6
CsCl
Both the cesium
and chlorine have 8
TiO2
Each titanium has
6, and each oxygen
has 3
Do they Conduct?
Conducting electricity means allowing
charges to move.
 In a solid, the ions are locked in place.
 Ionic solids are insulators.
 When melted, the ions can move around.
3. Melted ionic compounds conduct.
– NaCl: must get to about 800 ºC.
– Dissolved in water, they also conduct
(free to move in aqueous solutions)

- Page 198
The ions are free to move when they are
molten (or in aqueous solution), and thus
they are able to conduct the electric current.
Metallic Bonds are…
 How
metal atoms are held
together in the solid.
 Metals hold on to their valence
electrons very weakly.
 Think of them as positive ions
(cations) floating in a sea of
electrons: Fig. 7.12, p.201
Sea of Electrons
 Electrons
are free to move through
the solid.
 Metals conduct electricity.
+
+ + +
+ + + +
+ + + +
Metals are Malleable
 Hammered into shape (bend).
 Also ductile - drawn into wires.
 Both malleability and ductility
explained in terms of the
mobility of the valence
electrons
- Page 201
Due to the mobility of the
valence electrons, metals have:
1) Ductility and 2) Malleability
Notice
that the
ionic
crystal
breaks
due to ion
repulsion!
Malleable
Force
+
+ + +
+ + + +
+ + + +
Malleable

Mobile electrons allow atoms to slide
by, sort of like ball bearings in oil.
Force
+ + + +
+ + + +
+ + + +
Ionic solids are brittle
Force
+
+
-
+
+
+
+
-
+
+
Ionic solids are brittle

Strong Repulsion breaks a crystal apart,
due to similar ions being next to each
other.
Force
- + - +
+ - + - + - +
Crystalline structure of metal
 If
made of one kind of atom,
metals are among the simplest
crystals; very compact & orderly
 Note Fig. 7.14, p.202 for types:
1. Body-centered cubic:
–every atom (except those on
the surface) has 8 neighbors
–Na, K, Fe, Cr, W
Crystalline structure of metal
2. Face-centered cubic:
–every atom has 12 neighbors
–Cu, Ag, Au, Al, Pb
3. Hexagonal close-packed
–every atom also has 12 neighbors
–different pattern due to hexagonal
–Mg, Zn, Cd
Alloys
 We
use lots of metals every day,
but few are pure metals
 Alloys are mixtures of 2 or more
elements, at least 1 is a metal
 made by melting a mixture of the
ingredients, then cooling
 Brass: an alloy of Cu and Zn
 Bronze: Cu and Sn
Why use alloys?
Properties are often superior to the pure
element
 Sterling silver (92.5% Ag, 7.5% Cu) is
harder and more durable than pure Ag,
but still soft enough to make jewelry and
tableware
 Steels are very important alloys
– corrosion resistant, ductility, hardness,
toughness, cost

More about Alloys…
7.3, p.203 – lists a few alloys
 Types? a) substitutional alloy- the
atoms in the components are about
the same size
 b) interstitial alloy- the atomic sizes
quite different; smaller atoms fit into
the spaces between larger
 “Amalgam”- dental use, contains Hg
 Table