Ionic Compounds
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The joining of two atoms in a stable
arrangement
Elements gain, lose, or share electrons to
reach the electron configuration of the noble
gas closest to them in the periodic table
Two types of bonding
◦ Ionic bonds: result from the transfer of electrons
from one element to another
◦ Covalent bonds: result from the sharing of
electrons between two atoms
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A pure substance that cannot be broken
down into simpler substances by a chemical
reaction
Identified by a one- or two-letter symbol
Arranged in the periodic table
Its location on the periodic table indicates a
lot about its chemical properties
Can be a metal, nonmetal, or a metalloid
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Ionic bonds
◦ Form between a metal (left side of periodic table)
and a nonmetal (right side of periodic table
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Covalent bonds
◦ Form when two nonmetals combine
◦ Form when a metalloid bonds to a nonmetal
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Positively charged ions
Have fewer elections (e-) than protons
sodium atom
sodium ion
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Negatively charged ions
Has more e- than protons
◦
chlorine atom
chlorine ion
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A main group element is especially stable
when it possesses an octet of e- in its outer
shell
octet = 8 valence e−
the cation charge = the group number
group 1A:
M
1 valence e−
M + + e−
group 2A:
M
2 valence e−
M2+ + 2e−
group 3A:
M
3 valence e−
M3+ + 3e−
the anion charge = 8 – group number
group 6A:
group 7A:
+
X
6 valence e−
2e−
+ e−
X
7 valence e−
X
2−
charge = 8 – 6 = 2
X
−
charge = 8 – 7 = 1
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The sum of the charges in an ionic compound
must be zero overall
Ions will arrange to maximize anion-cation
attractions and minimize anion-anion and
cation-cation repulsions
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There must be two F- anions for each Ca+
cation to have an overall charge of zero
HOW TO Write a Formula for an Ionic Compound
Step [1]
Identify which element is the cation
and which is the anion.
Step [2]
Determine how many of each ion type is
needed for an overall charge of zero.
 When the cation and anion have different
charges, use the ion charges to determine the
number of ions of each needed.
Step [3]
To write the formula, place the cation
first and then the anion, and omit charges.
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Calcium Iodide
◦ Cation = calcium
 Charge 2+
◦ Anion = iodine
 Charge -
◦ Need two iodine for every calcium for an overall
charge of zero
◦ CaI2
“Criss-cross” rule
 Make magnitude of charge on one ion into
subscript for other
 When doing this, make sure that subscripts are
reduced to lowest whole number.
Al3+ O2–
Al2O3
Main group cations are named for the element from
which they are formed.
Na+
sodium
K+
potassium
Ca2+
calcium
Mg2+
magnesium
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Systematic name
◦ Follow the name of the cation by a Roman numeral
in parentheses to indicate its charge
Fe2+
iron(II)
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Fe3+
iron(III)
Common name
◦ Use suffic “-ous” for the cation with a smaller
charge and suffix “-ic” for the cation with a higher
charge
Fe2+
Fe3+
ferrous
ferric
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Anions are named by replacing the ending of
the element name by the suffix “-ide.”
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Name the cation and then the anion
Do not specify the charge on the ion
Do not specify how many ions of each type
are needed to balance charge
Na+
+
sodium
Mg2+
+
magnesium
F−
fluoride
Cl−
chloride
NaF
sodium fluoride
MgCl2
magnesium chloride
HOW TO Name an Ionic Compound
Step [1]
Determine the charge on the cation.
Step [2]
Name the cation and the anion
 If the cation could be multiple charges indicate
the charge with roman numerals or with a
–ous / -ic suffix.
Step [3]
Write the name of the cation first then the
name of the anion
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K 2O
◦ Cation = K+
◦ Anion = O2◦ Potassium Oxide
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LiBr
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SnO
◦ Cation = Li+
◦ Anion = Br◦ Lithium Bromide
◦ Cation = Sn2+
◦ Anion = O2◦ Tin (II) Oxide /Stannous Oxide
HOW TO Derive the Formula from the Name of
an Ionic Compound
Step [1]
Identify the cation and the anion.
Step [2]
Determine the charge on the cation and anion.
Step [3]
Balance the charges.
Step [4]
Write the formula with the cation first and
use subscripts to communicate charge
balance.
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Cobalt (II) Oxide/Cobaltous Oxide
◦ Cation = Co
◦ Anion = O2◦ CoO
2+
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Iron(III) Fluoride/Ferric Flouride
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Beryllium Chloride
◦ Cation = Fe3+
◦ Anion = F◦ FeF3
◦ Cation = Be2+
◦ Anion = Cl◦ BeCl2
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Ionic compounds are crystalline solids with
very high melting and boiling points
When ionic compounds dissolve in water,
they separate into cations and anions,
increasing the conductivity of the solution

+
NaCl
water
solution
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A cation or anion
that contains more
than one atom
The multiple
atoms are held
together with
covalent bonds
The molecule has
an overall charge
associated with it
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When a cation and anion of equal charge
combine, only one of each ion is needed
Na+ + NO2−
NaNO2
zero overall
charge
Ba2+ + SO42−
BaSO4
zero overall
charge
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When a cation and anion of unequal charge
combine, use the ionic charges to determine
the relative number of each ion that is needed
Mg2+
+2 charge means
2 OH− anions are
needed.
+
OH−
Mg(OH)2
−1 charge means
1 Mg2+ anion is
needed.
zero overall
charge
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•
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The same rules are followed for naming
standard ionic compounds:
Name the cation and then the anion.
Do not specify the charge on the ions.
Do not specify how many ions of each type
are needed to balance charge.
•Use –ite suffix if 1 or less Oxygen atoms in anion
•Use –ate suffix if more Oxygen atoms in anion
•Use bi- prefix or write hydrogen if H part of anion
NaHCO3
Al2(SO4)3
sodium bicarbonate
aluminum sulfate