Naming and Writing
Formulas
for Compounds
Ionic Compounds
• Two Systems for naming:
1. Stock (Roman numerals)
2. Old System
Stock System
• Binary Compounds
1. Write the name of the
positive ion 1st
2. Check to see if it has
more than one oxidation
#. If it does determine
the charge and use a
Roman numeral to
designate the charge
3. Write the root name of
the negative ion. Change
the ending to an –ide
ending.
•
Compounds with
Polyatomic ions
1. Same steps as binary
for positive ion
2. For negative ion, just
write the name of the
polyatomic
*** DO NOT ADD THE
ENDING –IDE
Determining Charge for Ions with
Variable Oxidation #’s
--Ions w/ more
than one oxidation
# (transition
metals, groups 312)
1. Hg
2. Cu
3. Pb
4. Sn
5. Cr
6. Fe
***Note: Zn is +2
Ag is +1
• Assign an oxidation # to the
negative ion
Ex. Hg Cl-1
Multiply the oxidation # by the
subscript
Ex. Hg Cl-1
1
Since the compound is neutral the
overall charge must = 0
Ex. Hg+1 Cl-1 = 0
1
1
+1-1 = 0
Remember…. Roman
numerals are only used
for those ions with more
than one charge!!!!!!!!
1.NaCl
2.SrCl2
3.NaOH
4.CuCl2
5.PbO2
6.CuOH
7.HgBr2
8.Al2O3
9.SrO
10.HgO
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Sodium Chloride
Strontium chloride
Sodium hydroxide
Copper (II) chloride
Lead (IV) oxide
Copper (I)
hydroxide
Mercury (II) bromide
Aluminum oxide
Strontium oxide
Mercury (II) oxide
Old System
1. Write the name of
the positive ion 1st.
Check to see if the
ion has more than
one oxidation #. If
it does, determine
the charge and add
one of the
following endings
a) –ous for lower
b) -ic for higher
Remember…
-ous is less
-ic is more
2. Write the root of
the negative ion
3. Add –ide if it is an
element
4. Write the name of
the ion if it is a
polyatomic
Old System Names
•
•
•
•
•
Cu +1
Hg+1
Fe+2
Pb+2
Sn+2
cuprous
mercurous
ferrous
plumbous
stannous
•
•
•
•
•
Cu+2
Hg+2
Fe+3
Pb+4
Sn+4
cupric
mercuric
ferric
plumbic
stannic
1.
2.
3.
4.
5.
6.
7.
Hg(OH)2
SnCl2
PbO
CuCl
FeO
Fe2O3
HgOH
1.
2.
3.
4.
5.
6.
7.
Mercuric hydroxide
Stannous chloride
Plumbous oxide
Cuprous chloride
Ferrous oxide
Ferric oxide
Mercurous hydroxide
1. Write the symbols for the ions side by side, with
the positive ion 1st
2. Cross over charges diagonally to give subscripts
(Subscripts tell how many of each element are in the
compound).
3. Check the subscripts to make sure the
compound is neutral.
4. Do not write subscripts that are 1 (they are
understood)
5. Do not write subscripts that are the same #
6. If the subscripts are divisible by the same #,
reduce them to give the simplest ratio
7. If the compound contains a polyatomic ion that
will have a subscript from crossing over, you
must PUT PARENTHESIS AROUND IT!!!!
Examples
•
Write the formula for:
Write the formula for:
Magnesium Oxide
Strontium Chloride
1. Sr+2 Cl -1
1. Mg +2 O-2
2. SrCl2
2. MgO
**subscripts that are 1
are not written
** subscripts that are the
same # are not written
More Examples
• Write the formula
for:
• Write the formula
for:
Lead (IV) oxide
** remember, the Roman numeral
Stannic sulfate
tells you the oxidation #
Pb+4 O-2
Pb2O4 (these can be reduced)
PbO2
Sn +4 SO4-2
(the –ic ending tells you that it is
tin’s higher charge)
Sn(SO4)2
** the subscripts can be reduced
and sulfate must have
parenthesis because it is a
polyatomic ion and it has a
subscript that will be written
Write the formulas for:
•
•
•
•
•
•
•
•
Lithium bromide
Strontium sulfide
Aluminum oxide
Mercury (II)
hydroxide
Plumbic carbonate
Ferrous oxide
Ferric oxide
Ammonium sulfate
• Write the name of the
least electronegative
• ONLY USED FOR
element 1st.
NAMING COVALENTLY
BONDED COMPOUNDS • A prefix is used w/the
name of the 1st element
(Remember… this will
only if more than one
be two nonmetals
atom is present
bonded together)
• The second element
always get a prefix
• Then write the root and
add -ide
Numerical Prefixes for Binary
Molecular
Number
1
2
3
4
5
6
7
8
9
10
Prefix
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca
Examples
• Name:
1. N2O
Dinitrogen monoxide
2. NO
Nitrogen monoxide
3. N2O3
Dinitrogen trioxide
Writing Formulas for Binary
Molecular
• Use the
prefixes to tell
you how many
of each element
is in the
compound.
• Examples:
1. Disulfur trioxide
S2O3
2. Carbon monoxide
CO
3. Carbon
tetrachloride
CCl4
Recognizing Acids
• At this very beginning level, you will
recognize an acid by the fact that its
formula starts with H, as in these
examples:
• HCl
HNO3
H2SO4
HClO3
H3BO3
The name of an acid is derived from its anion:
• For acids in which the anion is an
element, the name of the acid begins
with the prefix hydro- The acid’s name also includes the root
name of the anion and the word acid
• In addition, you must change the
suffix of the anion to –ic
• Ex: HCl
– Hydrochloric Acid
• For acids in which the anion
is a polyatomic, the prefix
hydro- IS NOT USED!!!
• Write the name of the
polyatomic and:
-Change –ate to –ic (or to –
oric/-uric for a few
cases)
-And -ite to -ous
• Then write the word acid.
• Name the following acids:
•
•
•
•
•
•
1) H3PO4
2) H2CO3
3) H2SO4
4) HIO3
5) HF
6) HNO2
1)Phosphoric Acid
2)Carbonic Acid
3)Sulfuric Acid
4)Iodic Acid
5)Hydrofluoric Acid
6)Nitrous Acid
***Remember… the prefix hydro- means
its an element bonded with hydrogen, no
hydro- means it’s a polyatomic
Write the formula for these acids:
• hydrobromic acid
• nitric acid
• sulfurous acid
• phosphorous acid
• acetic acid
1.HBr
2.HNO3
3.H2SO4
4.H3PO3
5.HC2H3O2