Unit 6 – Ionic Bonding
Ionic Compounds
(Metallic Substances)
Forming Chemical Bonds
•
Chemical Bond – force that holds two
atoms together
1. Positive nucleus to negative electrons
–
Molecules
2. Positive ion attracted to negative ion
–
Ionic Compound
Forming Chemical Bonds
• Molecules and Molecular Compounds
– Molecule – electrically neutral unit of a
substance that retains the properties of the
substance.
– Molecular compound – compound made of
individual molecules.*
• 2 or more nonmetals
• Low melting and boiling points – tend to be
liquids or gases at room temperature
Forming Chemical Bonds
• Ions and Ionic Compounds
– Ion – atom or group of atoms with a charge.
• Cation – positive charge caused by a loss of
electrons to become more stable. (Metals)
• Anion – negative charge caused by a gain of
electrons to become more stable. (Nonmetals)
– Ionic compound – neutral compound composed
of cations and anions.*
• Made of metal and nonmetal
• High melting and boiling points – usually solids at
room temperature
Forming Chemical Bonds
•
Chemical Formula – kinds and number of
atoms in the smallest representative unit of
a compound.
1. Molecular Formula – kind and number of
atoms in a molecule.
–
H2O or C6H12O6
2. Formula Unit – lowest whole-number ratio of
ions in the ionic compound.
–
NaCl, MgCl2, or (NH4)2SO4
Forming Chemical Bonds
• Monatomic ions – 1 atom ions
– Using the periodic table to find charges
• Noble gases are stable
• Atoms will gain or lose to obtain the
same number of electrons as the
nearest noble gas.
• Anions ending changes to “-ide”
Forming Chemical Bonds
Element
#
e-
Nearest
noble
gas
Noble
gas e-
Ne
10
Mg
12
Cl
17
Ar
Al
13
Ne
# Gain
or lost Formula
eLoss 2
Mg2+
18
Gain 1
Cl-
10
Loss 3
Al3+
Formation and Nature of Ionic
Bonds
Ionic compound formation
1Cl
Cl
Al
+
Cl
Cl
3+
Al
+
1Al Cl3
Cl
1Cl
Formation and Nature of Ionic
Bonds
Ionic compound formation
2O
O
3+
Al
Al
+
O
2+
O
3+
Al
Al
O
2O
Al2O3
Formation and Nature of Ionic
Bonds
Properties of ionic compounds
•
•
•
•
•
•
Crystalline solids with high melting points
Brittle
Usually metal and nonmetal in compound
Highly water soluble
Nonconductor as a solid
Conductor when a molten or aqueous
(electrolyte)
Formation and Nature of Ionic
Bonds
• Lattice Energy – energy needed to separate
electrons (1 mole) from the ionic compound
– Smaller atoms have higher lattice energies
• More shells and shielding make lower lattice
energies
– Greater charged ions have higher lattice
energies
Names and Formulas for Ionic
Compounds
• Transition Metal Ions
– Many transition metals can be stable at several
charges.
• Fe2+, Fe3+, Cu+, Cu2+, Hg2+2, Hg+2, Sn2+, Sn4+, Pb2+,
and Pb4+!
– Use roman numerals and parenthesis to
distinguish between different ions.
Fe2+
iron (II)
2+
Fe3+
iron (III)
3+
Names and Formulas for Ionic
Compounds
• Polyatomic ions – a group of atoms with a
charge.
– Look them up on the table
– Examples:
Ammonium cation
(NH
NH4)++
Sulfate anion
(SO
SO4)2-2-
Names and Formulas for Ionic
Compounds
The formula of an ionic
compound is the fewest cations and
anions needed to make the total
charge zero.
Names and Formulas for Ionic
Compounds
What is the formula of sodium chloride,
table salt?
Sodium = Na+
Chloride = Cl-
Na+
Cl-
+1
-1
NaCl
=0
Names and Formulas for Ionic
Compounds
What is the formula of iron(III) sulfate?
iron(III) = Fe3+
sulfate = (SO4)2Fe3+
Fe3+
+3
+3
+6
(SO4)2- (SO4)2- (SO4)22-6
2=0
Fe2(SO4)3
2-
Criss-Cross Reduce
1. Criss-cross the charge values as subscripts
2. Reduce if you can
iron(III) sulfate
tin(IV) oxide
Fe3+
Sn4+
2
(SO4)2-
3
2 and 3 can’t be reduced!
Fe2(SO4)3
O2-
2
4
1
2
2 and 4 can be reduced to 1 and 2
SnO2
Names and Formulas for Ionic
Compounds
Naming Ionic Compounds
1.
2.
Name the cation 1st and anion 2nd.
Copy the names of the ions from the back of the
periodic table.
• Monatomic cations use the element name.
• Monatomic anions use the root of the element name
plus the suffix -ide.
• If an element can have more than one charge state,
use a Roman numeral in parentheses after the
element name, for example, iron (II) to indicate the
Fe2+ ion. You may have to use the charge and the
number of anions to figure out which charge the
cation is in!
Names and Formulas for Ionic
Compounds
• What is the name for MgO?
Mg2+ and O2magnesium oxide
• What is the name of CuSO4?
Cu+ or Cu2+ and (SO4)2copper (II) sulfate
Use your anion charge
and number to figure
it out!
2. Metallic Substances
1
2
a. Metallic bond- force of attraction between
free floating valence electrons and
positively charged metal ions. (electron
sea)1,2
Delocalized electrons
b. Properties of metals
around the cations
–
–
–
–
Usually solids
Usually high melting point
Good conductor of heat and
electricity
Malleable, ductile, and shiny
2. Metallic Substances
c. Alloy - mixture of two or more elements
(1 must be a metal).
d. Types of alloys
•
Substitutional – atoms of metal are replaced
by atoms of similar size
•
•
Sterling silver, brass, 10-carat gold
Interstatial – small atoms put in between
metal atoms
•
Carbon steel
Bonding
Review
Ionic Bonding
Metallic Bonding