Ionic compounds consist of a positive metal ion and a negative nonmetal ion combined in a proportion such that their charges add up to a net charge of zero.
NaCl – consists of one Na + and one Cl .
Monatomic ions consists of a single atom with a positive or negative charge resulting from the loss or gain of one or more valence electrons.

Cations tend to lose valence electrons. (1+ charge – lose 1 electron, 2+ charge – lose 2 electrons, etc. )
When the metals in Groups 1A, 2A, and 3A lose electrons, they form cations with positive charges equal to their group number.
The name of the cations of the Group 1A, 2A and 3A are the same as the name of the metal, followed by the word ion or
cation.
Na + is sodium ion, Ca 2+ is calcium ion, Al 3+ is aluminum ion.

Nonmetals tend to gain electrons to form anions , so the charge of a nonmetallic ion is negative.
The charge of any ion of a Group A nonmetal is determined by subtracting 8 from the group number.
Group 7A form anions with a 1 charge (7-8 = -1)
Anion names start with the stem of the element name and end in –ide .
Anion of fluorine is fluoride ion (F ), anion of chlorine is chloride ion (Cl )

Many of the transition metals (Group 1B – 8B) form more than one cation with different ionic charges.
Two methods are used to name these ions.
1. Stock System – a roman numeral in parentheses is placed after the name of the element to indicate the numerical value of the charge.
Fe 2+ is iron(II) ions Fe 3+ is iron(III) ion.
2. Classical – name of the element is used to form the root name for the element.
Fe 2+ is ferr ous ion Fe 3+ is ferr ic ions

Polyatomic Ions are composed of more than one atom.
Sulfate ions (SO
4
2) is composed of one sulfur atom and four oxygen atoms.
Polyatomic ions are a tightly bound group of atoms that behave as a unit and carry a charge.
The names of most polyatomic anions end in
–ite or
–ate
.

CO
3
2-
SO
3
2-
S
2
O
3
2-
Chromate
Peroxide
PO
3
3-
ASO
3
3-
BO
3
3-
P
2
O
7
4-
Common Polyatomic Ions
Charge 2 -
Carbonate Oxalate
Sulfite
Thiosulfate
SO
4
2-
SiO
3
2-
Cr
2
O
7
2CrO
4
2-
O
2
2-
Phosphite
Arsenite
Charge 3 -
PO
4
3-
ASO
4
3-
Borate
Charge 4 -
Pyrophosphate
C
2
O
4
2-
Sulfate
Silicate
Dichromate
Phosphate
Arsenate

A binary compound is composed of two elements and can be either ionic or molecular (covalent).
To name any binary ionic compound, place the cation name first, followed by the anion name.
Cs
2
O is cesium oxide
Cu
2
O is copper(I) oxide
NaBr is sodium bromide
CuO is copper(II) oxide

Write the symbol of the cation and then the anion. Add whatever subscripts are needed to balance the charges.
The positive charge of the cation must balance the negative charge of the anion so that the net ionic charge of the formula is zero.
K + + Cl -

KCl
Ca 2+ + Br -

CaBr
2
Fe 3+ + O 2-

Fe
2
O
3
Use the crisscross method – the numerical value of the charge of each ion is crossed over and becomes the subscript for the other ion.

An –ate or –ite ending on the name of a compound indicates that the compound contains a polyatomic anion that includes oxygen.
Write the symbol for the cation followed by the formula for the polyatomic ion and balance the charges.
Ca 2+ + NO
3
-
Sr 2+ + SO
3
2-

Ca(NO
3
)
2

SrSO
3
Li + + CO
3
2-

Li
2
CO
3
Use the crisscross method – the numerical value of the charge of each ion is crossed over and becomes the subscript for the other ion.

First recognize that the compound contains a polyatomic ion.
State the cation first and then the anion
NaC l
O sodium hypochlorite
(NH
4
)
2
C
2
O
4 ammonium oxalate
Li
2
CO
3 lithium carbonate

Binary ionic compounds are composed of the ions of two elements, a metal and a nonmetal.
Binary molecular compounds are composed of two elements, two nonmetals and they are not ions.
Binary molecular compounds are composed of molecules, not ions, so ionic charges cannot be used to write formulas or to name them.
In addition, when two nonmetallic elements combine, they often do so in more than one way. (CO, CO
2
)
Prefixes in the names of binary molecular compounds help distinguish compounds containing different amounts of the same two elements.

The prefix in the name of a binary molecular compound tells how many atoms of each element are present in each molecule of the compound.
Prefix monoditritetrapentahexaheptaoctanonadeca-
Number
1
2
3
4
5
6
7
8
9
10

The names of all binary molecular compounds end in
–ide.
CO is carbon monoxide
CO
2 is carbon dioxide
If just one atom of the first element is in the formula, omit the prefix mono-
•Name the elements in order listed in the formula
•Use prefixed to indicate the number of each kind of atom
•The suffix of the name of the second element is –ide.
N
2
O is dinitrogen monoxide
SF
6 is sulfur hexafluoride.

Use the prefixes in the name to tell you the subscript of each element in the formula.
Then write the correct symbols for the two elements with the appropriate subscripts.
Dinitrogen tetraoxide
N
2
O
4
Diphosphorus trioxide
P
2
O
3

Acid is a compound that contains one or more hydrogen atoms and produces hydrogen ions (H+) when dissolved in water.
When naming acids, the acid consists of an anion combined with as many hydrogen ions as needed to make the molecule electrically neutral.
The general chemical formulas of acids is H n
X.
X is a monatomic or polyatomic anion n is a subscript indication the number of hydrogen ions combined with the anion.

Three rules are used to name acids. The name depends on the name of the anion and its suffix (-ide, -ite, -ate)
1. a. When the name of the anion ends in –ide , the acid name begins with the prefix hydro.
H b. The stem of the anion has the suffix
–ic and is followed by the word acid.
+ + Cl -

HCl
Hydrogen ion chlor ide ion hydro chlor ic acid
H + + S 2-

H
2
S
Hydrogen ion sulf ide ion hydro sulfur ic acid

Three rules are used to name acids. The name depends on the name of the anion and its suffix (-ide, -ite, -ate)
2. a. When the anion name ends in –ite , the acid name is the stem of the anion with the suffix –ous, followed by the word acid
H + + SO
3
2-

H
2
SO
3
Hydrogen ion sulf ite ion sulfur ous acid
H + + IO
2
-

HIO
2
Hydrogen ion iod ite ion iod ous acid

Three rules are used to name acids. The name depends on the name of the anion and its suffix (-ide, -ite, -ate)
3. a. When the anion name end in –ate , the acid name is the stem of the anion with the suffix –ic followed by the word acid.
H + + NO
3
-

HNO
3
Hydrogen ion nitr ate ion nitr ic acid
H + + SO
4
2-

H
2
SO
4
Hydrogen ion sulf ate ion sulfur ic acid

Use the rules for writing the names of acids in reverse to write the formula for acids.
Hydro brom ic acid
H ydro indicates the brom ide ion
HBr
Phosphor ous acid
ous indicates the phosph ite ion
H
3
PO
3 phosphor ic acid
-ic and beginning with the anion name indicates the phosph ate ion
H
3
PO
4

A base is an ionic compound that produced hydroxide ions (OH ) when dissolved in water.
Bases are named the same way as other ionic compounds – the name of the cation is followed by the name of the anion.
NaOH is sodium hydroxide
To write the formulas for bases, write the symbol for the cation followed by the formula for the hydroxide ion.
(then use the crisscross method to write the formula as you do as you do for any ionic compound)
Aluminum hydroxide – Al 3+ + OH -

Al(OH)
3
Ammonium hydroxide – NH
4
+ + OH -

NH
4
OH