CHAPTER 7,8
CHEMICAL BONDS
CHAPTER 7
CHEMICAL BONDS
6.1
6.2
6.3
6.4
• IONIC BONDING
• COVALENT BONDING
• NAMING COMPOUNDS & WRITING FORMULAS
• THE STRUCTURE OF METALS
Objectives
Ionic Bonding
Identify when an atom is unlikely to react
Identify one way in which elements can
achieve stable electron configurations
Determine how the structure of an ionic
compound affect its properties
CHAPTER 7
Ionic Bonding
CHEMICAL BONDS
Bonding
 Why are Noble Gases inert (nonreactive)?
 Stable electron configuration – the highest occupied energy level
of the noble gas atom is filled.
 Eight valence electrons in the case of all Noble gases
 Except Helium(He), which has two…however is still filled
 Other elements tend to react to achieve the same stable electron
configuration as the Noble Gases…
filled outermost energy levels.
CHAPTER 7
CHEMICAL BONDS
Ionic Bonding
Electron Dot Diagrams
 An electron dot diagram is a model of an atom in which each dot
represents a valence electron, and the element symbol represents
the nucleus and all other electrons of the atom.
 Examples:
CHAPTER 7
CHEMICAL BONDS
Ionic Bonding
Ionic Bonds – Transfer of Electrons
 Atoms of elements that do not have a complete set of valence electrons
tend to react with other atoms to form stable electron configurations.
 Some elements do this by a transfer of electrons: Ionic bonding.
 When an atom gains or loses electrons, the number of protons and
electrons is no longer equal. It now has a net positive or negative
charge and is an ion. An ion is a charged atom.
CHAPTER 6
CHEMICAL BONDS
Ionic Bonding
Ionic Bonds – Formation of Ions
Cations = Positve Charge
 If an ion has more protons than
electrons, it has a net positive
charge, and is called a cation.
 Represented by a superscript plus
sign to the right of the element
symbol. Example : Na+
 Named after their elements. For
example, Na+ is called the sodium
ion.
Anions = Negative Charge
 If an ion has more electrons than
protons, it has a net negative
charge, and is called a anion.
 Represented by a superscript minus
sign to the right of the element
symbol. Example : Cl Named by using part of the element
name plus the suffix -ide. For
example, Cl- is called the chloride
ion.
CHAPTER 6
CHEMICAL BONDS
Ionic Bonding
CHAPTER 6
CHEMICAL BONDS
Ionic Bonding
Formation of Ionic Bonds
 OPPOSITES ATTRACT: Once ions are
formed from the transfer of electrons, the
positive and negative ions are attracted to
each other and form chemical bond.
 A
chemical bond is the force that holds
atoms or ions together as a unit.
 An ionic
bond is the force that holds anions
and cations together.
CHAPTER 6
CHEMICAL BONDS
Ionic Bonding
CHAPTER 7
CHEMICAL BONDS
Ionic Bonding
Ionization Energy
 For an atom to lose an electron, the electron must gain
enough energy to overcome its attraction to the positive
nucleus.
 The amount of energy required to remove an electron is
called ionization energy. It varies from element to
element.
 The lower the ionization energy (IE), the easier it is to
remove an electron from an atom.
CHAPTER 7
CHEMICAL BONDS
Ionization Energies of the
A Group Elements
• Which group has the highest
ionization energies? Why?
• Which group has the lowest
ionization energies? Why?
• Which element has the lowest
ionization energy? Why?
• Which element has the highest
ionization energy? Why?
Ionic Bonding
CHAPTER 7
Ionic Bonding
CHEMICAL BONDS
Ionic Compounds
 Ionic compounds (contain ionic bonds) can be
represented by chemical formulas
 Chemical Formula:
• Shows elements in a compound with element symbols
• Gives ratios of atoms or ions in the compound via subscripts
• If only one atom of an element is present, no subscript is
required
 Examples: NaCl MgCl2
CHAPTER 7
CHEMICAL BONDS
Ionic Bonding
Properties of Ionic Compounds
 Tend to form crystal lattices (repeating patterns of ions resulting




from attractions between positive and negative ions.)
Properties of ionic compounds can be explained by strong
attractions among ions in a crystal lattice.
High melting point (a lot of energy required to break attractions
between ions.)
Solid state is brittle (pushing like ions together causes them to
repel in a “rebound effect”)
Solid has poor conductivity (ions can’t move), but liquid state has
high conductivity (ions can move)
CHAPTER 7
CHEMICAL BONDS
Ionic Bonding
Bonding Basics Worksheet
1.
Write the electron dot diagram (Lewis Structure) for each element.
2.
Use one color for the electrons in metals, and another color for the
electrons in nonmetals.
3.
Draw an arrow (or more if needed) with a different color to show the
transfer of electrons, and move the colored dot to the new location.
4.
Determine the charge for each ion and write the formula.
5.
Make sure the sum of the oxidation numbers is zero and write
chemical formula.
the
Objectives
Covalent Bonding
Determine how atoms are held together in a
covalent bond
Identify what happens when atoms don’t share
electrons equally
List the factors that determine whether a
molecule is polar
Compare and contrast the attractions between
polar and nonpolar molecules
CHAPTER 8
CHEMICAL BONDS
Covalent Bonding
Covalent Bonds
 Covalent Bonds (Co- means “to share” / -valent refers to valence electrons)
 Chemical bond in which two atoms share a pair of valence electrons
 Attractions between shared electrons and the protons in each nucleus hold the
atoms together
 Molecule: a neutral group of atoms joined by one or more covalent bonds
 Multiple covalent bonds: sometimes 2 atoms can share more than one pair of
electrons
 2 shared pairs: double bond (4 electrons total are shared )
 3 shared pairs : triple bond (6 electrons are shared)
O O O2
CHAPTER 8
CHEMICAL BONDS
Covalent Bonding
Covalent Bonds
 Representation (example: hydrogen gas, or H2)
 Electron Dot diagram
 Structural Formula (dash represents a pair of shared electrons)
 For Multiple bonds, multiple lines between two atoms would be used.
ELECTRON DOT DIAGRAM
H H
CHAPTER 8
Covalent Bonding
CHEMICAL BONDS
Covalent Bonds
 Representation (example: hydrogen gas, or H2)
 Electron Dot diagram
 Structural Formula (dash represents a pair of shared electrons)
 For Multiple bonds, multiple lines between two atoms would be used.
ELECTRON DOT DIAGRAM
HH
CHAPTER 8
Covalent Bonding
CHEMICAL BONDS
Covalent Bonds
 Representation (example: hydrogen gas, or H2)
 Electron Dot diagram
 Structural Formula (dash represents a pair of shared electrons)
 For Multiple bonds, multiple lines between two atoms would be used.
ELECTRON DOT DIAGRAM
HH
Shared Electrons
CHAPTER 8
CHEMICAL BONDS
Covalent Bonding
Polar vs Nonpolar Bonds
 Unequal sharing of electrons
 Some atoms have a greater attraction for electrons
 Electronegativity: the ability of an atom to attract electrons to itself in a covalent
bond.
 Polar Covalent Bond
 Electrons shared UNEQUALLY between 2 atoms
 The two atoms have DIFFERENT electronegativities
 Nonpolar Covalent Bond
 Electrons shared EQUALLY between 2 atoms
 The two atoms have SIMLAR electronegativities.
CHAPTER 8
Covalent Bonding
CHEMICAL BONDS
Polar Molecules
 Polar molecules have partial positive and negative charges at opposite ends
(like a magnet has North and South poles)
 Partial negative charge: δ Partial positive charge:δ+
 Polarity of a molecule is determined by
 Type of covalent bonds (polar or nonpolar)
 Shape of molecule
Polar molecule
Nonpolar molecule
CHAPTER 8
CHEMICAL BONDS
Covalent Bonding
Attraction Between Molecules
 All molecules have a force of attraction between them.
 Attractions between polar molecules like water, are stronger than those
between nonpolar molecules
 In water, these attractions are called hydrogen bonds (partial positive hydrogen
ends attract partial negative oxygen ends)
 This explains many of water strange and
important properties:
 High surface tension
 High adhesion and cohesion
 Lower density in solid state (ice floats!)
Objectives
Naming Compounds &
Writing Formulas
List the information that the name and
formula of an ionic compound provide
Determine what information does
the name and formula of a
molecular compound provide
CHAPTER 7
CHEMICAL BONDS
Naming Compounds &
Writing Formulas
Naming Ionic Compounds
 A compound made from only two elements is a binary ionic
compound.
 Naming ionic compounds is easy:
 It’s the name of the cation (positive ion)
 Followed by the name of anion (negative ion), it has the suffix –ide.
 Let’s take calcium and iodine as an example:
Calcium is the name of the cation and,
iodide is the name of the anion, therefore:
calcium iodide
CHAPTER 7
Naming Compounds &
Writing Formulas
CHEMICAL BONDS
Writing Ionic Compounds
 Once again let’s look at calcium iodide:
 What are their oxidation numbers?
 Cross them (only the numbers…no charges!)
 Don’t write ones!
 Rewrite the formula
+2
-1
Ca
I
CaI2
CHAPTER 7
CHEMICAL BONDS
Naming Compounds &
Writing Formulas
Describing Ionic Compounds
 The following are two substances, both made with compounds of
copper and oxygen.
Copper (I) oxide – Cu2O
Copper (II) oxide – CuO
 The name of an ionic compound must distinguish the compound from
other ionic compounds containing the same elements.
CHAPTER 7
CHEMICAL BONDS
Naming Compounds &
Writing Formulas
Metals with Multiple Ions
 Remember an Ion is: a charged atom
 Many transition metals form more than one type of ion.
 When a metal forms more than one ion, the name of the ion
contains a Roman numeral to indicate the charge on the ion.
CHAPTER 7
Naming Compounds &
Writing Formulas
CHEMICAL BONDS
Copper and Oxygen
Copper (I) oxide
Copper (II) oxide
+1
-2
+2
-2
Cu
O
Cu
O
Cu2O
Cu2O2
CuO
CHAPTER 7
CHEMICAL BONDS
Naming Compounds &
Writing Formulas
Polyatomic Ions
 A polyatomic ion is a covalently bonded group of atoms that has a positive or
negative charge, and acts as a single unit (like an ion).
 The prefix poly- means many
 Most polyatomic ions are anions,
which means they will have a
negative charge.
 Sometimes parentheses are used
in a formula to denote the number
of polyatomic ions are included
within that formula.
CHAPTER 7
Naming Compounds &
Writing Formulas
CHEMICAL BONDS
Naming & Writing Compounds with Polyatomic Ions
 Let’s look at calcium and phosphate (a polyatomic ion)
 NOTHING CHANGES!, follow the same steps as before!
 What are their oxidation numbers?
 Cross them. (Only the numbers, NO CHARGES)
 Don’t write ones!
 Rewrite the formula.
 Use parentheses if necessary
 The name of this compound is:
calcium phosphate
+2
Ca
-3
PO4
Ca
Ca33(PO
PO424)2
CHAPTER 7
CHEMICAL BONDS
Naming Compounds &
Writing Formulas
Math Practice
1.
Write the formula for the compound calcium oxide.
2.
Write the formula for the compound copper(I) sulfide.
3.
Write the formula for the compound sodium sulfate.
4.
Write is the name of the compound whose formula is NaOH?
CaO
Cu2S
Na2SO4
sodium hydroxide
CHAPTER 8
CHEMICAL BONDS
Naming Compounds &
Writing Formulas
Describing Molecular Compounds
 Molecular compounds are those compounds formed by sharing




electrons, covalently bonded.
The name and formula of a molecular compound describe the
type and number of atoms in a molecule of the compound.
The general rule is the most metallic element appears first in the
name.
If both elements are in the same group, the more metallic
element is closer to the bottom of the group.
The name of the second element is changed to end in the suffix
–ide. (as in carbon dioxide)
CHAPTER 8
CHEMICAL BONDS
Naming Compounds &
Writing Formulas
Naming Molecular Compounds
Number
of Atoms
Prefix
used to denote the number of atoms of each element
within the molecule.
• The prefix mono- is often is not used for the first
element in the name.
1
mono-
2
di-
3
tri-
4
tetra-
N2O4
5
penta-
6
hexa-
7
hepta-
8
octa-
9
nona-
10
deca-
• When naming molecular compounds prefixes are
dinitrogen tetroxide
CHAPTER 8
CHEMICAL BONDS
Naming Compounds &
Writing Formulas
Naming Molecular Compounds
P2O5
diphosphorus pentoxide
CO
carbon monoxide
Number
of Atoms
Prefix
1
mono-
2
di-
3
tri-
4
tetra-
5
penta-
6
hexa-
7
hepta-
8
octa-
9
nona-
10
deca-
CHAPTER 8
CHEMICAL BONDS
Naming Compounds &
Writing Formulas
Writing Molecular Compounds
Number
of Atoms
Prefix
1
mono-
2
di-
CF4
3
tri-
4
tetra-
5
penta-
pentaphosphorus decoxide
6
hexa-
7
hepta-
8
octa-
9
nona-
10
deca-
carbon tetrafluoride
P5O10
CHAPTER 8
CHEMICAL BONDS
The Structure of Metals
What are the forces that give a metal
its structure as a solid?
How do metallic bonds produce some
of the typical properties of metals?
How are the properties of alloys
controlled?