• An ionic compound is composed of cations and anions.
• Ions are arranged in a repeating three-dimensional
pattern, forming a crystal.
• The formula of an ionic compound gives the smallest
possible integer number of ions in the substance
(without writing charges) so that the combination is
electrically neutral.
• The formula gives the formula unit of the compounds.
A formula unit is not a molecule!
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• What is formula of the ionic compound
of Mg2+ and N3-?
The common multiple of the charges is 6, so we need
three Mg2+ and two N3-. The resulting formula is
Mg3N2
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• What is the formula of the ionic
compound of Ca2+ and PO43-?
The common multiple of the charges is 6, so we need
three Ca2+ and two PO43-. The resulting formula is
Ca3(PO4)2
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• Organic Compounds
• An important class of molecular substances;
they contain carbon combined with other
elements – notably hydrogen, oxygen, and
nitrogen.
• Hydrocarbons contain only carbon and
hydrogen.
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• A functional group is a reactive portion of a
molecule that undergoes predictable
reactions.
Functional Group
OH
O
O
C
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Name of
Group
Examples
Alcohol
Methyl alcohol
Ether
Dimethyl ether
Carboxylic acid
Acetic acid
OH
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• Chemical nomenclature is the systematic
naming of chemical compounds.
• Compounds that are not organic are called
inorganic compounds.
Carbon monoxide, carbon dioxide, carbonates, and
cyanides are also classified as inorganic
compounds.
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• Naming Inorganic Compounds
1.Name the cation.
2.Name the anion.
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• Monatomic ions
• Ions formed from a single atom.
• Common monatomic ions are listed on the
next slide by group and by period.
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Common Monatomic Ions of the
Main-Group Elements
Period
IA
IIA
IIIA
IVA
VA
VIA
VIIA
H-
1
2
Li+
Be2+
3
Na+
Mg2+
4
K+
5
6
N3-
O2-
F-
Al3+
S2-
Cl-
Ca2+
Ga3+
Se2-
Br-
Rb+
Sr2+
In3+
Sn2+
Te2-
I-
Cs+
Ba2+
Tl3+,
Tl+
Pb2+
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Bi3+
2|9
•
Rules for Predicting the Charge on a
Monatomic Ion
•
1. Most main-group metals have one
monatomic ions with a charge equal to the
group number.
Al, in Group IIIA(3), has one ion, Al3+.
Sr, in Group IIA(2), has one ion, Sr2+.
K, in Group IA(1), has one ion, K+.
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•
2. Some main-group metals with high atomic
number have more than one cation. One cation
will have the charge of the group number minus
2; the second cation will have a charge equal to
the group number
Pb in Group IVA(14) has two ions:
Pb2+ and Pb4+
Tl in Group IIIA(13) has two ions:
Tl+ and Tl3+
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•
3. Most transition metals form more than one
cation, of which one is +2.
Zn and Cd form only the +2 ion.
Ag forms only the +1 ion.
•
4. Nonmetal main-group elements form one
monatomic anion with a charge equal to the
group number minus 8.
F in Group VIIA(17) forms the F- ion.
S in Group VIA(16) forms the S2- ion.
N in Group VA(15) forms the N3- ion.
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• Naming Monatomic Ions
• Monatomic cations are named after the
element if the element forms only one cation.
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• If more than one cation forms:
a.In the Stock system, the charge is written using a
Roman numeral and is enclosed in parentheses.
Cu2+ is copper(II).
Cu+ is copper(I).
b.In an older system, the suffic –ic (for the highercharged cation) or –ous for the lower-charged
cation) is added to the element’s stem.
Cu2+ is cupric.
Cu+ is cuprous.
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• Fe3+ is iron(III) or ferric ion.
• Fe2+ is iron(II) or ferrous ion.
• Hg2+ is mercury(II) or mercuric ion.
• The second ion mercury forms is diatomic:
• Hg22+ is mercury(I) or mercurous ion.
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• Cr3+ is chromium(III) or chromic ion.
• Cr2+ is chromium(II) or chromous ion.
• Mn2+ is manganese(II) or manganous ion.
• Co2+ is cobalt(II) or cobaltous ion.
• Zinc forms only Zn2+, so it is called zinc ion.
• Cadmium forms only Cd2+, so it is called cadmium
ion.
• Silver forms only Ag+, so it is called silver ion.
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• Polyatomic Ion
• An ion consisting of two or more atoms
chemically bonded together and carrying an
electrical charge.
• Table 2.5 lists common polyatomic ions.
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• What are the names of the following
ionic compounds?
– BaO
– Cr2(SO4)3
BaO is barium oxide.
Cr2(SO4)3 is chromium(III) sulfate or chromic
sulfate.
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• What are the chemical formulas for the
following ionic compounds?
– potassium carbonate
– manganese(II) sulfate
The ions K+ and CO32- form K2CO3
The ions Mn2+ and SO42- form MnSO4
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• Binary Molecular Compounds
• A compound composed of only two elements.
• Binary compound of a metal and a nonmetal
are generally named using ionic rules.
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• Naming Binary Molecular Compounds
• We usually name the elements in the order given
in the formula.
• Name the first element using the element name.
• Name the second element using the element root
+ -ide suffix.
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• Add a prefix to each name to indicate the number of
atoms of that element. The prefix mono- is used only
when needed to distinguish two compounds of the
same two elements.
• The final vowel of the prefix is often dropped when
followed by an element name that begins with a vowel.
Oxygen is the most common example.
N2O4
NO
dinitrogen tetroxide (“a” is dropped)
nitrogen monoxide (only one “o”)
(also called nitric oxide)
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•
•
•
•
•
•
•
•
•
•
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Prefixes (Greek)
One (1)
monoTwo (2)
diThree (3)
triFour (4)
tetraFive (5)
pentaSix (6)
hexaSeven (7)
heptaEight (8)
octaNine (9)
nonaTen (10)
deca2 | 24
• Some compounds have common names that
differ from their systematic names:
H2S
H2O
NH3
hydrogen sulfide (the “di” is omitted)
water
ammonia
• Common names need to be memorized.
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• Acids and Corresponding Anions
• Oxoacids contain hydrogen, oxygen, and a
third central atom.
• To name an acid from its anion name:
1.Change an –ate suffix to –ic.
2.Change an –ite suffix to –ous.
3.Add the word “acid.””
• For example:
HNO3
H2SO4
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nitric acid
sulfuric acid
2 | 26
Oxoanion
CO32-
Oxoacid
H2CO3
NO2-
carbonate
ion
nitrite ion
HNO2
carbonic
acid
nitrous acid
NO3-
nitrate ion
HNO3
nitric acid
PO43-
phosphate ion
H3PO4
SO32-
sulfite ion
H2SO3
SO42-
sulfate ion
H2SO4
phosphoric
acid
sulfurous
acid
sulfuric acid
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Oxoacid
Oxoanion
ClOClO2ClO3ClO4-
hypochlorite
ion
chlorite
ion
chlorate
ion
perchlorate
ion
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HClO
HClO2
HClO3
HClO4
hypochlorous
acid
chlorous
acid
chloric
acid
perchloric
acid
2 | 28
• What are the names of the following
compounds?
– OF2
– S4N4
– BCl3
OF2 is oxygen difluoride
S4N4 is tetrasulfur tetranitride
BCl3 is boron trichloride
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• What are the formulas for the following
binary molecular compounds?
– carbon disulfide
– nitrogen tribromide
– dinitrogen tetrafluoride
The formula for carbon disulfide is CS2.
The formula for nitrogen tribromide is NBr3.
The formula for dinitrogen tetrafluoride is N2F4.
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• Bromine has an oxoacid, HBrO2, bromous
acid (compare to HClO2, chlorous acid).
What are the name and formula of the
corresponding anion?
The anion corresponding to HBrO2 is
bromite, BrO2-.
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• Hydrate
• A compound that contains water molecules
weakly bound in the crystals.
• The formula of a hydrate is written with a dot
before the water molecule(s) included.
• For example:
CuSO45H2O
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• Hydrates are named using the anhydrous
(without water) compound name followed by
the prefix for the number of water molecules
included and the word “hydrate.”
• For example:
CuSO45H2O is named
copper(II) sulfate pentahydrate.
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• A compound whose common name is
green vitriol has the chemical formula
FeSO47H2O. What is the chemical name
of this compound?
FeSO47H2O is iron(II) sulfate heptahydrate.
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• Calcium chloride hexahydrate is used to
melt snow on roads. What is the
chemical formula of the compound?
The chemical formula for calcium chloride
hexahydrate is CaCl26H2O.
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