Ionic and Metallic Bonding

1
Chapter 7

• Ionic and Metallic Bonding

2
Section 7.1 Ions
3
Valence Electrons

• Valence electrons electrons in the highest
  occupied energy level (n2, 3, 4, etc)
• Valence electrons are the ones involved in
  chemical bonds
• How many valence electrons does C have?
• How many valence electrons does arsenic have?

7.1
4
Electron Dot Structures

• Show valence electrons as dots

Na
Mg
1 valence e-
2 valence e-
Al
Si
P
S
Cl
3
4
5
6
7
Ar
8
7.1
5
The Octet Rule

• The Octet Rule in forming compounds atoms tend
  to achieve the electron configuration of a noble
  gas. Noble gases have 8 electrons in their outer
  energy levels.

Octet
3p
ENERGY
3s
Argon
Ar
8
2p
2s
1s
7.1
6
Formation of Cations

• Loss of valence electrons gains octet in
  next-lowest energy level
• Naming same as metal

Same as configuration of Ne
Mg2
Mg
Mg 2
ENERGY
ENERGY
3s
3s
2p
2p
2s
2s
Magnesium ion
1s
1s
7.1
7
Transition metal cations
Mn2

• May not follow the octet rule
• May form multiple ions

3d
4s
3p
ENERGY
3d
3s
Mn7
4s
3p
3d
4s
3s
3p
Mn
3s
7.1
8
Transition metal cations

• Pseudo noble gas configuration

ENERGY
ENERGY
4d
4d
5s
5s
4p
4p
4s
4s
Ag
Ag
1s22s22p6 3s23p63d104s24p64d10
Filled orbitalsmore stable
7.1
9
Questions on Cations

• How many electrons will Ca lose in forming a
  cation?
• What is the symbol (with charge for this ion)?
• What is the electron configuration for this ion?

7.1
10
Formation of Anions

• Gain of valence electrons gains octet in next
  highest energy level
• Naming add -ide

Same as configuration of Ne
N3-
N
ENERGY
ENERGY
2p
2p
2s
Nitride ion
2s
1s
1s
7.1
11
More on anions

• Example Halogens Fluorine, create the
  fluoride ion
• Electron Dot diagram?
• How many valence electrons is fluorine missing?

7.1
12
Questions on Anions

• How many electrons would O gain in forming an
  anion?
• What is the name of this ion?
• What is the ions electron configuration?

7.1
13
Homework

• Complete the Ion Worksheet
• Monday you will get the Chapter 7 packet
• Come with questions about the Ion Worksheet

14
Bellwork, Tuesday November 18th

• How many electrons will each element gain or lose
  in forming an ion?
• calcium
• aluminum
• fluorine
• oxygen
• lithium
• phosphorus

15
Ionic compounds

• Ionic compounds compounds composed of anions and
  cations
• Whole compound is electrically neutral
• Ionic bonds electrostatic forces that hold ions
  together

-
Cl
K
2
Ca
-
I-
K
Cl
I
7.2
16
When cations and anions form bonds with each
other they are called SALTS
SALTS

• Example
• Li
• 1s 2p
• F
• 1s 2p

Li
LiF
F-
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Ionic Compounds (contd)

• Chemical formula kinds and numbers of atoms in
  the smallest representative unit of a substance,
  i.e. caffeine is C8H10N4O2
• Formula unit Lowest whole number ratio of ions
  in a compound
• Potassium iodide 1 K and 1 I-
• Formula unit KI
• Calcium chloride1 Ca2 and 2 Cl-
• Formula unit CaCl2

7.2
18
Writing Formulas

• Write the formulas for the binary ionic compounds
  formed between the following elements
• Magnesium and iodine
• Write the symbol for the ions side by side
• Cross over the charges to give subscripts
• Check the subscripts and divide by their largest
  CF.

19
Crisscross Method

• Calcium and Chlorine
• Rubidium and Nitrogen
• Aluminum and Oxygen

20
Transition Metal Ions

• Many transition metals can form two or more
  different cations.
• Iron (II) and Iron (III) are examples,
  Iron (II) Fe2 Iron (III) Fe3

21
Properties of Ionic Compounds

• Usually form solid crystals at room temperature
• Crystal repeating three dimensional patterns
• Strong attractive forces result in high melting
  points

7.2
22
Properties of Ionic Compounds

• Coordination number number of ions of opposite
  charge that surround the ion in a crystal
• Ionic compounds conduct electricity when melted
  or dissolved in water

7.2
23
- Page 198
Coordination Numbers
Both the sodium and chlorine have 6
NaCl
Both the cesium and chlorine have 8
CsCl
Each titanium has 6, and each oxygen has 3
TiO2
24
- 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.
25
Ionic Compounds

• What is the formula unit of the compound formed
  when Ba reacts with S?
• What is the formula unit of the compound formed
  when iron reacts with oxygen (if iron becomes
  Fe(III)?

7.2
26
Homework

• Complete the Worksheet
• Work on Chapter 7 packet
• page 196 12 13
• page 199 14, 15, 18-20, 22

27
Bellwork, Thursday November 20th

• Write the chemical formula for the following
  elements
• calcium and oxygen
• Aluminum and fluorine
• Lithium and nitrogen
• Carbon and bromine

28
7.3 Metallic Bonds
29
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

30
Sea of Electrons

• Think of them as positive ions (cations) floating
  in a sea of electrons
• Electrons are free to move through the solid.
• Metals conduct
  electricity.

31
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

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- Page 201
Due to the mobility of the valence electrons,
metals have
Notice that the ionic crystal breaks due to ion
repulsion!
1) Ductility
2) Malleability
and
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Malleable
Force
34
Malleable

• Mobile electrons allow atoms to slide by, sort of
  like ball bearings in oil.

Force
35
Ionic solids are brittle
Force
36
Ionic solids are brittle

• Strong Repulsion breaks a crystal apart, due to
  similar ions being next to each other.

Force
37
Crystalline structure of metal

• If made of one kind of atom, metals are among the
  simplest crystals very compact orderly
• Body-centered cubic
• every atom (except those on the surface) has 8
  neighbors
• Na, K, Fe, Cr, W

38
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

39
Alloys

• We use lots of metals every day, but very 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

40
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

41
More about Alloys

• Table 7.3, p.203 lists a few alloys
• substitutional alloy- the atoms in the components
  are about the same size
• interstitial alloy- the atomic sizes quite
  different smaller atoms fit into the spaces
  between larger

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All Due Wednesday

• 7.3 Book Assignment page 203 23-28, page 209
  83 NEW TODAY!
• Crisscross Worksheet (From Wed)
• 7.2 Book Assignment Page 196 12 13, page 199
  14, 15, 18-20, 22 (from Tue)
• Bond With a Classmate Activity/Worksheet (From
  Mon)
• Ion Worksheet (From Fri)
• Chapter 7 Packet
• Review Worksheet (Youll get tomorrow)