Chapter 7

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Chapter 7Ionic and Metallic Bonding
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Essential Question

• How do metals interact with nonmetals, and is
  this different than how they act with other
  metals?
• (By the end of this unit, you should be able to
  answer this question using all of the following
  vocabulary alloys, chemical formula,
  coordination number, electron dot structure,
  formula unit, halide ion, ionic bonds, ionic
  compounds, metallic bonds, octet rule, valence e-
  )

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Section 7.1 - Ions

• OBJECTIVES
• Determine the number of valence electrons in an
  atom of a representative element.

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Section 7.1 - Ions

• OBJECTIVES
• Explain how the octet rule applies to atoms of
  metallic and nonmetallic elements.

5
Section 7.1 - Ions

• OBJECTIVES
• Describe how cations form.

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Section 7.1 - Ions

• OBJECTIVES
• Explain how anions form.

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1.14.11

• Bellringer Do you think Chlorine (Cl) atoms are
  dangerous? Sodium (Na) atoms? Explain why or why
  not.
• (Once youve done that, start a page for notes)
• Objectives. SWBAT
• Determine VALENCE e- in a rep. element
• Use OCTET RULE
• Homework

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Before we go on

• Questions about tests/finals
• Do you have your Cornell notes ready?

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What type of e- are in an atom?

• The e- responsible for the chemical properties of
  atoms are those in the outer energy level.
• Valence e- ? The s and p electrons in the
  highest occupied energy level
• Core e- ? e- in energy levels below.

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Keeping Track of Electrons

• Atoms in the same column...
• Have the same outer electron configuration.
• So, the same of valence e-.
• The number of valence electrons is easily
  determined. It is the group number for a
  representative element!!
• Group 2A Be, Mg, Ca, etc.
• all have 2 valence electrons

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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 dont pair up until they have to (Hunds
  rule)

X
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The Electron Dot diagram for Nitrogen

• Nitrogen has 5 valence electrons to show.
• First we write the symbol.

N

• 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.

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The Octet Rule

• In Chapter 6, we learned that noble gases are
  generally unreactive in chemical reactions
• In 1916, Gilbert Lewis used this fact to explain
  why atoms form certain kinds of ions and
  molecules
• 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

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1.14.11

• BR Draw electron dot diagrams for the following
  atoms, then use arrows to show the e- leaving or
  entering the atom
• Li (Lithium, group 1a)
• I (Iodine, group 7a)
• F (Fluorine, group 7a)
• Ne (Neon, group 8a)
• Homework 7.2 reading notes (Ill check 7.1 and
  7.2 on Tuesday)

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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 (same as Neon) with 8 electrons in
  the outer level.

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Electron Dots For Cations

• Metals will have few valence electrons (usually 3
  or less) calcium has only 2 valence electrons

Ca
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Electron Dots For Cations

• Metals will have few valence electrons
• Metals will lose the valence electrons

Ca
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Electron Dots For Cations

• Metals will have few valence electrons
• Metals will lose the valence electrons
• Forming positive ions

Ca2
This is named the calcium ion.
NO DOTS are now shown for the cation.
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Electron Dots For Cations

• Lets do Scandium, 21
• The electron configuration is 1s22s22p63s23p64s23
  d1
• Thus, it can lose 2e- (making it 2), or lose 3e-
  (making 3)
• Sc ? Sc2

Sc
? Sc3
Scandium (III) ion
Scandium (II) ion
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Electron Dots For Cations

• Lets do Silver, element 47
• Predicted configuration is 1s22s22p63s23p64s23d10
  4p65s24d9
• Actual configuration is 1s22s22p63s23p64s23d104p6
  5s14d10
• Ag Ag1 (cant lose any more!!!)

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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

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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

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Electron Dots For Anions

• Nonmetals will have many valence electrons
  (usually 5 or more)
• They will gain electrons to fill outer shell.

3-
P
(This is called the phosphide ion, and should
show dots)
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Stable Electron Configurations

• All atoms react to try and achieve a noble gas
  configuration.
• Noble gases have 2 s and 6 p electrons.
• 8 valence electrons already stable!
• This is the octet rule (8 in the outer level is
  particularly stable).

Ar
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Exit Slip

• Write the electron dot configurations for the
  following
• Strontium
• Chlorine
• Aluminum
• Sodium
• Use arrows to show loss or gain of e-, and add
  charges

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Bellringer

• Predict the ions formed from the following
  elements
• Mg, N, K, F, B, Ca, Cl
• Take out your 7.1 reading notes
• Complete 7.2 reading notes for tomorrow

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Section 7.2 Ionic Bonds and Ionic Compounds

• OBJECTIVES
• Explain the electrical charge of an ionic
  compound.

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Section 7.2 Ionic Bonds and Ionic Compounds

• OBJECTIVES
• Describe three properties of ionic compounds.

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Ionic Bonding

• Anions and cations are held together by opposite
  charges ( and -)
• Ionic 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 (loss and gain)
• Electrons are transferred to achieve noble gas
  configuration.

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Ionic Compounds

1. Also called SALTS
2. Made from a CATION with an ANION (or literally
   from a metal combining with a nonmetal)

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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.
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Ionic Bonding
Na
Cl -
Note Remember that NO DOTS are now shown for the
cation!
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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).

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Ionic Bonding
Ca
P
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Ionic Bonding
Ca2
P
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Ionic Bonding
Ca2
P
Ca
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Ionic Bonding
Ca2
P 3-
Ca
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Ionic Bonding
Ca2
P 3-
Ca
P
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Ionic Bonding
Ca2
P 3-
Ca2
P
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Ionic Bonding
Ca
Ca2
P 3-
Ca2
P
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Ionic Bonding
Ca
Ca2
P 3-
Ca2
P
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Ionic Bonding
Ca2
Ca2
P 3-
Ca2
P 3-
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Ionic Bonding
P3-
Ca2
If you want to predict ionic bonding quickly
Ca3P2
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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
46
Ionic Bonding
Cl-
Na
Another example both have single charges
NaCl
47
Ionic Bonding
F-
Mg2
REMEMBER If you want to predict ionic bonding
quickly
Mg F2
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Ionic Bonding
O2-
Ti4
But be careful! It can be like balancing a
fraction! TiO2, not Ti2O4
Ti O2
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Properties of Ionic Compounds

• Crystalline solids - a regular repeating
  arrangement of ions in the solid Fig. 7.9, page
  197
• Ions are strongly bonded together.
• Structure is rigid.
• High melting points
• Coordination number- number of ions of opposite
  charge surrounding it

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- 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
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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.
• Melted ionic compounds conduct.
• NaCl must get to about 800 ºC.
• Dissolved in water, they also conduct (free to
  move in aqueous solutions)

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- 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.
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Beginning of Semester 2

• Take out your section assessments questions, your
  worksheets, and your notes staple them together
  (With notes on top)

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Todays agenda

• Today
• Review 7.1 and 7.2
• Start 7.3
• Tomorrow
• Finish 7.3
• Practice unit 7
• Wednesday
• Quiz

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QUICK REVIEW OF 7.1

• Objectives
• Determine val e- in a rep element
• Explain how octet rule applied to metals and
  nonmetals
• Describe how cations and anions form

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QUICK REVIEW OF 7.1

• Objectives
• Determine val e- in a rep element
• How do we do this?

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QUICK REVIEW OF 7.1

• Objectives
• Explain how octet rule applied to metals and
  nonmetals

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QUICK REVIEW OF 7.1

• Objectives
• Describe how cations and anions form
• Positive vs. negative charges
• Metals/nonmetals/metalloids

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QUICK REVIEW OF 7.2

• Objectives
• Explain the electrical charge of a compound
• Describe three properties of ionic compounds

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QUICK REVIEW OF 7.2

• Objectives
• Explain the electrical charge of a compound
• What is the overall charge of an atom?

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QUICK REVIEW OF 7.2

• Objectives
• Explain the electrical charge of a compound
• What is the overall charge of an atom?
• What is the overall charge of an ion?

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QUICK REVIEW OF 7.2

• Objectives
• Explain the electrical charge of a compound
• What is the overall charge of an atom?
• What is the overall charge of an ion?
• What is the overall charge of an ionic compound?

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QUICK REVIEW OF 7.2

• Objectives
• Describe three properties of ionic compounds
• Crystalline structure
• High melting points
• Conductive in solution or when melted, NOT as a
  solid!!!

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- 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.
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Section 7.3Bonding in Metals

• OBJECTIVES
• Model the valence electrons of metal atoms.

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Section 7.3Bonding in Metals

• OBJECTIVES
• Describe the arrangement of atoms in a metal.

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Section 7.3Bonding in Metals

• OBJECTIVES
• Explain the importance of alloys.

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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

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Sea of Electrons

• Electrons are free to move through the solid.
• Metals conduct electricity.

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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
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Malleable

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

Force
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Ionic solids are brittle
Force
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Ionic solids are brittle

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

Force
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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

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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

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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

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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

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More about Alloys

• Table 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

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Bellringer (6 min)

• Predict the ions formed for the following,
  showing how theyre formed
• Ca O Fe(II)
• Al S Ti(IV)
• Predict the ionic compound formed when Al and O
  combine
• Predict the ionic compound formed when Ca and S
  combine
• Use your own words to explain why solid ionic
  compounds are different than solid metals

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Valence s-orbital size

• Lookingat thesize of the s-orbitalsWhich
  atoms valence e-are in thelargest s-orbital?

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Homework

• P. 207 30-51

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End of Chapter 7