MOLECULAR COMPOUNDS / IONIC COMPOUNDS
Naming Inorganic Compounds
• All compounds can be written as
a full name or as a chemical
formula. A formula provides a
short hand method of writing the
compound.
• sodium chloride  NaCl(s)
Naming Binary Molecular
Compounds
1) The full name of the first element in the
compound is used.
2) The ending of the name of the second
element in the compound is changed to
“ide” (both names written in lower case)
3) A system of prefixes is used to indicate
the number of each type of atom in the
compound.
Naming Binary Molecular Compounds
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1
2
3
4
5
monoditritetrapenta-
6
7
8
9
10
hexaheptaoctanonadeca-
GREEK PREFIX SYSTEM
[ NONMETAL WITH NONMETAL ]
Naming Binary Molecular
Compounds
4) The symbol for the elements are
written in the same order as they
appear in the name, followed by a
subscript number to indicate the
number of each atom in the
compound
Examples
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carbon dioxide
CO2
carbon monoxide
CO
iodine tribromide
IBr3
silicon tetrahydride
SiH4
diphosphorus pentasulfide P2S5
Naming Binary Ionic
Compounds
• The chemical formula of an ionic
compound represents the lowest
whole number ratio of the ions in
the crystal and it is called a
formula unit.
Naming Binary Ionic Compounds
1) Use the full name of the positive
ion first.
2) Put the name of the negative ion
last and change the ending to
“ide”
3) The name of an ionic compound
does not use prefixes to show the
number of ions present
Naming Binary Ionic Compounds
4) When writing formulas of binary
ionic compounds the symbol for
the elements are written in the
same order as they appear in the
name. Subscript numbers are
used to indicate the ratio of the
ions in the compound.
Naming Binary Ionic Compounds
5)The charges on the ions must
balance in the chemical formula,
since ionic compounds are
electrically neutral.
Examples of ionic compounds
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sodium chloride
magnesium chloride
sodium phosphide
silver sulfide
zinc nitride
NaCl
MgCl2
Na3P
Ag2S
Zn3N2
Criss-cross method
•
3+
Al and
Cl
• AlCl3
• Cu2+ and O2• CuO
Naming ionic compounds formed by
transition elements
• Some of the transition
elements can form more
than one common type of
ion.
Atomic #
symbol
26
3+
Fe
iron (III)
2+
Fe
iron (II)
ion charge
Stock name
Stock System
• The stock system uses Roman
numerals after the name of the
positive (metal) ion to indicate the
charge on that ion.
• Example: iron (II) oxide
• iron (III) oxide
Stock system examples
• Copper can be either Cu2+ or Cu+.
In combination with oxygen each
ion will form a different
compound.
• copper (II) oxide  CuO
• copper (I) oxide  Cu2O
The Classical System
• The classical system uses
different suffixes(endings) to
indicate the possible charges on
the ion.
The Classical System
• The ending “ic” indicates the higher of the
two possible charges.
• The ending “ous” indicates the lower of the
two possible charges.
• chromic refers to Cr3+
• chromous refers to Cr2+
• These endings are added to the name of
the transition element
Examples
• Write the formulas of chromic
nitride and chromous sulfide.
• CrN & CrS
• Write the names for Fe3P2 and
Mn3P4
• iron (II) phosphide
• manganese (IV) phosphide
Polyatomic ions
• Polyatomic ions consist of a
group of atoms combined
together which have an
overall charge.
Naming polyatomic ions
• Polyatomic ions, being
negative, are always written
last in the name of the formula,
except for ammonium (+), it is
written first.
Naming polyatomic ions
• When writing the formula for
compounds containing more than one
of a polyatomic ion, the symbol for
the ion must be written in brackets.
• A subscript number is added to
indicate the number of polyatomic
ions present in the compound.
Examples of polyatomic ions
• Ammonium sulfate NH4+ SO42• (NH4)2SO4
• Tin (II) nitrate
• Sn(NO3)2
Sn2+ NO3-
Hydrated compounds
• ionic compounds that have water
molecules associated with their
crystal structure.
• anhydrous compound:
–hydrates that lose water; usually a
different colour.
Hydrated molecular formula
copper sulfate pentahydrate
copper sulfate
Naming Hydrates
• When writing the formula for hydrated
crystal of an ionic compound a dot is
placed between the formula and the
number of water molecules.
• Greek prefixes used to indicate how many
water molecules are present.
• copper(II) sulfate pentahydrate
• CuSO4●5H2O
Acids and Bases
Acids
• Acids are compounds that
contain hydrogen atoms
covalently bonded to other
atoms to form a molecular
compound.
Bases
• Bases are ionic compounds that are
able to release hydroxide ions (OH-)
in solution.
• Bases react with acids to produce a
neutral solution of salt and water.
• HCl(aq) + NaOH(aq)―>H2O(l) +
NaCl(aq)
Naming Acids
• All acids will be considered as being
dissolved in water, ie. In aqueous solution
and this must always be indicated by
placing the subscript (aq) after the acid
formula.
• Acids can be named in two ways. Both
systems are equally acceptable to the
IUPAC.
IUPAC system
• The IUPAC system places the word
aqueous in front of the name of the acid,
named as if it were an ionic compound.
• Example: HCl (g) is named as hydrogen
chloride, but dissolved in water it becomes
an acid called aqueous hydrogen chloride,
and its formula is HCl (aq).
The classical system
• The names of hydrogen compounds when
named as ionic compounds will end in ide,
ate or ite.
• There are three naming rules based on
each of these three possible endings.
Rule 1
• When the name of the negative ion ends
in -ide the acid begins with the prefix
hydro- and the stem of the negative ion is
given the ending –ic, in place of –ide. This
is followed by the word acid.
• HCl(aq) would be named as hydrogen
chloride and so becomes hydrochloric
acid.
Examples
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HF(aq)
hydroflouric acid
HBr(aq)
hydrobromic acid
HI(aq)
hydroiodic acid
Rule 2
• When the negative ion ends in –ate the
acid name is the stem of the negative ion
given the ending –ic , in place of –ate ,
followed by the word acid.
• HClO3(aq) would be named hydrogen
chlorate and so becomes chloric acid.
Examples
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H2CO3(aq)
carbonic acid
HNO3(aq)
nitric acid
Rule 3
• When the negative ion ends in –ite the
acid name is the stem of the negative ion
given the ending –ous , in the place of –
ite, followed by the word acid.
• Example: HNO2(aq) would be named
hydrogen nitrite and so becomes nitrous
acid.
Examples
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H2SO3(aq)
sulphurous acid
HClO2(aq)
chlorous acid
Writing names of acids
• Writing names of the
acids is simply the
reverse of the rules
above.
Exceptions to the rules
• Acids which have sulf- or phosph- as
their roots have extra letters added to
make the name sound better.
• Sulf- has -ur added so that it becomes
sulfuric or sulfurous.
• Phosph- has –or added to it to become
phosphoric and phosphorous.
Exceptions to the rules
• When the formula for the acid contains
COO, the hydrogen atom is placed at the
end of the formula after the COO.
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ethanoic acid is written as CH3COOH
Oxalic acid is written H2OOCCOO or
HOOCCOOH / HO2C2O2H condensed
Benzoic acid HC6H5COO / C6H5COOH
• Always remember, when
writing the formula of an acid,
to indicate that it is an acid by
placing the subscript (aq) after
the formula.