CHEMISTRY
CHAPTER
7
Table Of Contents
Matter and Change
Chapter 7: Ionic Compounds
and Metals.
Section 7.1
Ion Formation
Section 7.2
Ionic Bonds and Ionic Compounds
Section 7.3
Names and Formulas for Ionic
Compounds
Section 7.4
Metallic Bonds and the Properties of
Metals
Click a hyperlink to view the corresponding slides.
SECTION
7.1
Ion Formation
SECTION
7.1
Exit
Ion Formation
Valence Electrons and Chemical Bonds
• Define a chemical bond.
• Describe the formation of
positive and negative ions.
• Relate ion formation to
electron configuration.
octet rule: atoms tend to
gain, lose, or share
electrons in order to acquire
eight valence electrons
chemical bond
cation
anion
• A chemical bond is the force that holds
two atoms together.
• Chemical bonds form by the attraction
between the positive nucleus of one atom
and the negative electrons of another atom.
Ions are formed when atoms gain or lose
valence electrons to achieve a stable octet
electron configuration.
SECTION
7.1
Ion Formation
Valence Electrons and Chemical Bonds
(cont.)
• Atom’s try to form the octet—the stable
arrangement of eight valence electrons in the
outer energy level—by gaining or losing valence
electrons.
• A positively charged ion is
called a cation.
SECTION
7.1
Ion Formation
Positive Ion Formation (cont.)
• Metals are reactive because they lose valence
electrons easily.
• Transition metals commonly form 2+ or 3+
ions, but can form greater than 3+ ions.
• Other relatively stable electron arrangements
are referred to as pseudo-noble gas
configurations.
1
SECTION
Ion Formation
7.1
SECTION
7.2
Ionic Bonds and Ionic Compounds
Negative Ion Formation
• An anion is a negatively charged ion.
• Nonmetal ions gain the number of electrons
required to fill an octet.
• Some nonmetals can gain or lose electrons to
complete an octet.
• Describe the formation of ionic bonds and the structure of
ionic compounds.
• Generalize about the strength of ionic bonds based on the
physical properties of ionic compounds.
• Categorize ionic bond formation as exothermic or
endothermic.
compound: a chemical combination of two or more different
elements
SECTION
7.2
Ionic Bonds and Ionic Compounds
SECTION
7.2
Ionic Bonds and Ionic Compounds
Formation of an Ionic Bond
ionic bond
ionic compound
crystal lattice
electrolyte
lattice energy
Oppositely charged ions attract each other,
forming electrically neutral ionic
compounds.
SECTION
7.2
Ionic Bonds and Ionic Compounds
• The electrostatic force that holds oppositely
charged particles together in an ionic compound
is called an ionic bond.
• Compounds that contain ionic bonds are called
ionic compounds.
• Binary ionic compounds contain only two different
elements—a metallic cation and a nonmetallic
anion.
SECTION
7.2
Ionic Bonds and Ionic Compounds
Properties of Ionic Compounds
Properties of Ionic Compounds (cont.)
• Positive and negative ions exist in a ratio
determined by the number of electrons
transferred from the metal atom to the non-metal
atom.
• The strong attractions among the positive and
negative ions result in the formation of the crystal
lattice.
• The repeating pattern of particle packing in an
ionic compound is called an ionic crystal.
• A crystal lattice is the three-dimensional
geometric arrangement of particles, and is
responsible for the structure of many minerals.
• Melting point, boiling point, and hardness
depend on the strength of the attraction.
2
SECTION
7.2
Ionic Bonds and Ionic Compounds
SECTION
7.2
Ionic Bonds and Ionic Compounds
Properties of Ionic Compounds (cont.)
Energy and the Ionic Bond
• In a solid, ions are locked into position and
electrons cannot flow freely—solid ions are poor
conductors of electricity.
• Reactions that absorb energy are endothermic.
• Reactions that release energy are exothermic.
• Liquid ions or ions in aqueous solution have
electrons that are free to move, so they conduct
electricity easily.
• An ion in aqueous solution that conducts
electricity is an electrolyte.
SECTION
7.2
Ionic Bonds and Ionic Compounds
SECTION
7.2
Ionic Bonds and Ionic Compounds
Energy and the Ionic Bond (cont.)
Energy and the Ionic Bond (cont.)
• The energy required to separate 1 mol of ions in
an ionic compound is referred to as the lattice
energy.
• Smaller ions form compounds with more closely
spaced ionic charges, and require more energy
to separate.
• Lattice energy is directly related to the size of the
ions that are bonded.
• Electrostatic force of attraction is inversely related
to the distance between the opposite charges.
• The smaller the ion, the greater the attraction.
• The value of lattice energy is also affected by
the charge of the ion.
SECTION
7.3
Names and Formulas for Ionic Compounds
• Relate a formula unit of an ionic compound to its
composition.
• Write formulas for ionic compounds and oxyanions.
• Apply naming conventions to ionic compounds and
oxyanions.
SECTION
7.3
Names and Formulas for Ionic Compounds
formula unit
monatomic ion
oxidation number
polyatomic ion
oxyanion
nonmetal: an element that is generally a gas or a
dull, brittle solid and is a poor conductor of heat and
electricity
In written names and formulas for ionic
compounds, the cation appears first,
followed by the anion.
3
SECTION
7.3
Names and Formulas for Ionic Compounds
SECTION
7.3
Names and Formulas for Ionic Compounds
Formulas for Ionic Compounds
Formulas for Ionic Compounds (cont.)
• When writing names and formulas for ionic
compounds, the cation appears first
followed by the anion.
• A formula unit represents the simplest
ratio of the ions involved.
• Chemists around the world need to
communicate with one another, so a
standardized system of naming compounds
was developed.
• Oxidation number, or oxidation state, is
the charge of a monatomic ion.
SECTION
7.3
Names and Formulas for Ionic Compounds
• Monatomic ions are one-atom ions.
SECTION
7.3
Names and Formulas for Ionic Compounds
Formulas for Ionic Compounds (cont.)
Formulas for Ionic Compounds (cont.)
• The symbol for the cation is always written
first, followed by the symbol of the anion.
• Polyatomic ions are ions made up of
more than one atom.
• Subscripts represent the number of ions of
each element in an ionic compound.
• Since polyatomic ions exist as a unit,
never change subscripts of the atoms
within the ion. If more than one polyatomic
ion is needed, place parentheses around
the ion and write the appropriate subscript
outside the parentheses.
• The total charge must equal zero in an ionic
compound.
SECTION
7.3
Names and Formulas for Ionic Compounds
Names for Ions and Ionic Compounds
SECTION
7.3
Names and Formulas for Ionic Compounds
Names for Ions and Ionic Compounds (Cont.)
• An oxyanion is a polyatomic ion composed of
an element (usually a non-metal), bonded to one
or more oxygen atoms.
4
SECTION
7.3
Names and Formulas for Ionic Compounds
Names for Ions and Ionic Compounds (Cont.)
SECTION
Names and Formulas for Ionic Compounds
7.3
Names for Ions and Ionic Compounds (Cont.)
• Chemical nomenclature is a systematic way of
naming compounds.
– Name the cation followed by the anion.
– For monatomic cations use the element name.
– For monatomic anions, use the root element name and
the suffix –ide.
– To distinguish between different oxidation states of the
same element, the oxidation state is written in
parentheses after the name of the cation.
– When the compound contains a polyatomic ion, name
the cation followed by the name of the polyatomic ion.
SECTION
7.4
Metallic Bonds and the Properties of Metals
SECTION
7.4
Metallic Bonds and the Properties of Metals
• Describe a metallic bond.
electron sea model
• Relate the electron sea model to the physical
properties of metals.
delocalized electron
• Define alloys, and categorize them into two basic
types.
metallic bond
alloy
Metals form crystal lattices and can be
modeled as cations surrounded by a “sea”
of freely moving valence electrons.
physical property: a characteristic of matter that
can be observed or measured without altering the
sample’s composition
SECTION
7.4
Metallic Bonds and the Properties of Metals
SECTION
7.4
Metallic Bonds and the Properties of Metals
Metallic Bonds and the Properties of
Metals
Metallic Bonds and the Properties of
Metals (Cont.)
• Metals are not ionic but share several
properties with ionic compounds.
• Within the crowded lattice, the outer energy
levels of metal atoms overlap.
• Metals also form lattices in the solid state,
where 8 to 12 other atoms closely surround
each metal atom.
• The electron sea model proposes that all
metal atoms in a metallic solid contribute their
valence electrons to form a "sea" of electrons.
• The electrons are free to move around and
are referred to as delocalized electrons,
forming a metallic cation.
5
SECTION
7.4
Metallic Bonds and the Properties of Metals
SECTION
7.4
Metallic Bonds and the Properties of Metals
Metallic Bonds and the Properties of
Metals (Cont.)
Metallic Bonds and the Properties of
Metals (Cont.)
• A metallic bond is the attraction of an
metallic cation for delocalized electrons.
• Metals are malleable because they can be
hammered into sheets.
• Metals are ductile because they can be
drawn into wires.
• Boiling points are much higher than melting
points because of the energy required to
separate atoms from the groups of cations
and electrons.
SECTION
7.4
Metallic Bonds and the Properties of Metals
Metallic Bonds and the Properties of
Metals (Cont.)
• Mobile electrons surrounding positively charged
nuclei make metals good conductors of electricity
and heat.
• As the number of delocalized electrons
increases, so does hardness and strength.
SECTION
7.4
Metallic Bonds and the Properties of Metals
Metal Alloys
• An alloy is a mixture of elements that has
metallic properties.
–Ex. Stainless steel, brass, cast iron
• The properties of alloys differ from the
elements they contain.
–Ex. Steel is iron mixed with at least one other
element. Some properties of iron are present, like
magnetism, but steel is stronger than iron.
SECTION
7.4
Metallic Bonds and the Properties of Metals
Metal Alloys (cont.)
SECTION
7.4
Metallic Bonds and the Properties of Metals
Metal Alloys (cont.)
• Substitutional alloys are formed when some
atoms in the original metallic solid are replaced
by other metals of similar atomic structure.
• Interstitial alloys are formed when small holes in
a metallic crystal are filled with smaller atoms.
6