Inorganic Compounds and Acids

Ionic Molecular Aqueous Acid

Binary Ionic

Compound

Ternary Ionic

Compound

Binary MolecularCompound

Binaryacid

Ternary acid

“Ternary” MolecularCompound

Lewis Symbols and Formulas of Ionic Compounds

Li+ [He]+ 1s2

Mg2+ [Ne]2+ 1s22s22p6

Al3+ [Ne]2+ 1s22s22p6

F- [Ne]2+ 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: AlF3.

Formulas of Ionic CompoundsThe 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- O2- F-

P3- S2- Cl- As3- Se2- Br-

I-

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+

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:

Formulas of Ionic Compounds

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

Ca3N2AlCl3 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 & Br Li+ & Br- LiBr Lithium bromide

2. How do K and N combine in an ion compound?

K & N K+ & N3- K3N 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 Fe2+ & Cl- FeCl2 or Fe3+ & Cl- FeCl3

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???

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 FeCl2 Copper (I) chloride CuCl

Iron (III) chloride FeCl3 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 FeCl2 Cuprous chloride CuCl

Ferric chloride FeCl3 Cupric chloride CuCl2

Naming Binary Ionic Compounds

Naming Binary Ionic Compounds

Polyatomic IonsA 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 Carbon monoxide CO2 Carbon dioxide SO2 Sulfur dioxide SO3 Sulfur trioxide CCl4 Carbon tetrachloride PCl5 Phoshorous pentachloride SF6 Sulfur hexafluoride N2O4 Dinitrogen tetroxide P4S7 Tetraphosphorous heptasulfide C. Some covalent compound have common names

H2O NH3 CH4

water ammonia 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 CO2N2O, NO, NO2, N2O3, N2O4, and N2O5

Nomenclature for Acids