Inorganic Compounds and Acids
Ionic
Binary
Ternary
Ionic
Ionic
Compound Compound
Molecular
Binary
Molecular
Compound
“Ternary”
Molecular
Compound
Aqueous Acid
Binary
acid
Ternary
acid
Lewis Symbols and Formulas of Ionic Compounds
Li+
Mg2+
[He]+
[Ne]2+
1s2
1s22s22p6
Al3+
F-
[Ne]2+
[Ne]2+
1s22s22p6
1s22s22p6
Fluorine accepts only one electron to achieve
its octet or ideal gas configuration.
Two fluorine atoms are thus required to accept the two electrons
that magnesium must lose to achieve its octet.
Using this information, the chemical formula of magnesium fluoride
can be predicted to be: MgF2.
Aluminum fluoride must be: AlF 3.
Formulas of Ionic Compounds
The formulas of all binary ionic compounds between the group
IA, IIA, and IIIA metals, and the group VA, VIA, and VIIA
nonmetals can be predicted using these principles.
Group IA metals lose 1 electron to form 1+ ions.
Group IIA metals lose 2 electrons to form 2+ ions.
Group IIIA metals lose 3 electrons to form 3+ ions.
Group VA nonmetals gain 3 electrons to form 3- ions.
Group VIA nonmetals gain 2 electrons to form 2- ions.
Group VIIA nonmetals gain 1 electron to form 1- ions.
Ionic Compounds
A. Charges on Monoatomic Ions
1. For non-metallic elements, charges can be related to
position on the periodic table
N3-
P3-
As3-
O2-
S2-
Se2-
FClBrI-
2. Fixed-charge metals
Alkali metals(Group IA):
Li+, Na+, K+, Rb+, Cs+
Alkaline earths(Group IIA):
Be2+, Mg2+, Ca2+, Sr2+, Ba2+
Others:
Ag+,
Zn2+, Al3+ Formulas of Ionic Compounds
When cations and anions combine to form a binary salt or
acid, they always do so in such a way that the net charge of
the substance formed is zero.
The easiest way to apply this principle is the cross over
approach, as illustrated for aluminum oxide:
The magnitude of the charge on
each ion is used as the subscript
for the other ion in the formula
for the substance.
NaCl
Na2O
Na3N
CaCl2 CaO
Ca3N2
AlCl3
Al2O3 AlN
B. Principles of Nomenclature for Ionic Compounds
1. Loss or gain of electrons does not occur without the complementary process.
2. Positive and negative ions combine in a ratio which achieves charge neutrality.
3. The formula for an ionic compound must reflect the charge neutrality.
4. After the formula is determined, the compound is named based on the metal and
nonmetal elements present.
Charges are not indicated for main group elements.
C. Examples with fixed-charge metals:
1. How do Li and Br combine in an ionic compound?
Li &
Li+ & Br-
LiBr
Lithium bromide
2. How do K and N combine in an ion compound?
Br
K
&
N K+
& N3- K 3N
Potassium nitride
3. How do Al and O combine in an ionic compound?
Al &
O
Al3+ & O2- Al2O3
Aluminum oxide
Naming Binary Ionic Compounds
In the name of a binary ionic compound,
1. The cation is always given first and the anion second.
2. The cation is always specified as the name of the metal.
3. The anion is specified by using the first part of the name
of the nonmetal and then adding the suffix “ide”.
4.
Sodium chloride (NaCl)
Aluminum oxide (Al2O3)
Magnesium sulfide (MgS).
Nomenclature for Variable-charged metals
A. Examples
Fe2+ or
Fe3+
Pb2+ or Pb4+
Co2+ or Co3+ Which ion is referred to must be determined from the name or formula of the compound.
B. Examples
1. How do Fe and Cl combine in an ionic compound ?
Fe & Cl How do you distinguish between these ?
FeCl2 is the formula for
iron (II) chloride
FeCl3 is the formula for
iron (III) chloride
What do the “II” and the “III” represent???
Fe2+ & Cl- or
Fe3+ & Cl- FeCl2
FeCl3
Naming Binary Ionic Compounds
Transition metals in period 4 and higher can often have several
possible stable positive ions:
Fe2+ and Fe3+
Cu+ and Cu2+
For this reason, names such as iron chloride and copper chloride
are ambiguous.
The modern system for naming the salts of these types of metal ions
indicates the charge on the cation as a roman numeral within
the name of the substance:
Iron (II) chloride
Iron (III) chloride
FeCl2
FeCl3
Copper (I) chloride
CuCl
Copper (II) chloride
CuCl2
An older system, still in common use, uses the suffixes –ous and –ic
to indicate the less positive and more positive cations:
Ferrous chloride
Ferric chloride
FeCl2
FeCl3
Cuprous chloride
CuCl
Cupric chloride
CuCl2
Naming Binary Ionic Compounds
Polyatomic Ions
A polyatomic ion is two or more atoms chemically combined
into a single charged unit:
Naming Covalent (Molecular) Compounds
A. Covalent compounds do not always combine in readily predictable ratios.
B. Prefixes are therefore used to indicate the number of atoms involved.
CO
CO2
SO2
SO3
CCl4
PCl5
SF6
N2O4
P4S7
Carbon monoxide
Carbon dioxide
Sulfur dioxide
Sulfur trioxide
Carbon tetrachloride
Phoshorous pentachloride
Sulfur hexafluoride
Dinitrogen tetroxide
Tetraphosphorous heptasulfide
C. Some covalent compound have common names
H2O
NH3
water
ammonia
CH4
methane
Nomenclature for Binary Molecular Compounds
The systematic method for naming simple, binary molecular
compounds is based on the fact that some pairs of elements can
form more than one covalently bonded compound.
Common examples are:
CO and CO2
N2O, NO, NO2, N2O3, N2O4, and N2O5
Nomenclature for Acids