Chapter 7 - Chemical Formulas and Chemical
Compounds
Hemoglobin
• Where are the metals on the periodic table?
• Where are the nonmetals on the periodic
table?
• What is a cation? An anion?
• What are the charges of elements in groups 1,
2, and 13 based on their number of valence
electrons?
• What are the charges of elements in groups
15, 16, and 17 based on their number of
valence electrons ?
Warm-Up
Significance of a Chemical Formula –
Different for Molecular and Ionic Compounds
• Molecular: The number
of atoms contained in a
single molecule of the
compound.
• Ionic: The number of
ions in one formula unit,
the simplest ratio of
cations and anions.
Chemical Formulas
Molecular: Octane - C8H18
A hydrocarbon; consists of only
carbon and hydrogen
Ionic: Aluminum sulfate - Al2(SO4)3
The parentheses are used to indicate
that there are 3 polyatomic sulfate
anions in the formula unit. If there
is no subscript, the value is
understood to be 1.
How many atoms total for each? 26 and 17,
respectively
Monotomic Ions
Monatomic
Ions
Definition
Steps in
Creating
the
Formula
How Do
You Name
It?
Example
Ions formed
from a single
atom. Main
group ions
form to a
noble gas
configuration
No formulas—
just ions!!
For cations:
The element
name.
For anions:
The ending of
the name is
dropped and
the ending –
ide is added.
Cation Ex. Ca
is calcium;
Ca+2 is
Calcium
Anion Ex. F is
flourine; F-1 is
flouride
Examples: Naming Ions
Write the symbol and the name of the ion
most typically formed by
Element Ion
Ion name
K
K+
potassium cation
Ca
Ca2+
calcium cation
S
S2sulfide anion
Cl
Clchloride anion
Binary Ionic Compounds
Binary Ionic
Compounds
Definition
Steps in Creating the
Formula
How Do You Name
It?
Example
Compounds
composed of two
elements: a
metal and a
nonmetal)
1. Write the symbols
and charges of the
ions side by side,
cation first.
Al3+ O2−
2. Cross over the
charges by using the
absolute value of
each ion’s charge as
the subscript for the
other ion. Make sure
that the total
charges now add up
to zero.
Al23+ O32−
3. The reason for
this is so that the
number of electrons
that are being given
by the cation can be
received by the
anion(s).
Al2O3
1. Use the name of
the cation first
2. Then use the
anion name, but
drop the ending
and add –ide
Note: You are
basically just
naming the
monatomic ions
separately and
then putting them
together
Al2O3
Aluminum
Oxide
The total charge
must be equal to
zero.
• Write the formula for the binary ionic
compounds formed between the following
elements:
• Zinc and iodine
ZnI2
• Zinc and sulfur
ZnS
• Sodium and sulfur
Na2S
• Aluminum and nitrogen AlN
• Potassium and iodine
KI
EXAMPLE: Binary Ionic Compounds
• Name the binary ionic compounds from
their formula:
• AgCl
silver chloride
• CaCl2
calcium chloride
• ZnO
zinc oxide
• CaBr2
calcium bromide
• SrF2
strontium fluoride
• Al2S3
aluminum sulfide
EXAMPLE: Naming Binary Ionic Compounds
Transition metals
Transition
Metals
USE THE
STOCK
SYSTEM OF
NAMING
(Roman
numerals
indicate the
charge)
Definition
Steps in
Creating the
Formula
How Do You
Name It?
Example
D-block
elements (and
the metals
under the
staircase)
When naming
ionic
compounds
with
transition
metals, you
MUST write
the charge of
the metal in
Roman
numerals
Transition
metals can
have more
than one
charge (No
formulas)
The name
won’t change
(ex. Fe=iron=
iron, no matter
what the
charge)
Use Roman
numerals after
the name of
the metal to
indicate the
charge.
PbCl2
Determine the
charge of the
metal using
the known
charge of your
negative ion
Lead (II)
chloride
Pb(SO4)2
Lead (IV)
Sulfate
• Write the formula and give the name for the
compounds that form between:
•
•
•
•
•
Cu2+ and BrSn2+ and FHg2+ and S2Fe2+ and O2Fe3+ and O2-
CuBr2
SnF2
HgS
FeO
Fe2O3
copper(II)bromide
tin(II)fluoride
mercury(II)sulfide
iron(II)oxide
iron(III)oxide
EXAMPLE: Stock System of Naming
• give the name for the following
compounds:
CuO
FeS
CoF3
SnI4
copper(II)oxide
iron(II)sulfide
cobalt(III)fluoride
tin(IV)iodide
EXAMPLE: Stock System of Naming
Compounds With Polyatomic Ions
Compounds
containing
Polyatomic Ions
Definition
Steps in
Creating the
Formula
How Do You
Name It?
Example
Ionic compounds
that use one or two
positive or negative
polyatomic ions to
form ionic
compounds
Another note: Are
produced by the loss
of hydrogen ions
(H+) from oxyacids:
Sulfuric acid H2SO4
Sulfate
SO42−
You basically use
the same steps as
with putting two
monatomic ions
together.
THE TOTAL
POSITIVE CHARGE
WILL BALANCE THE
TOTAL NEGATIVE
CHARGE.
Except in this case,
you won’t be
changing the ending
of the oxyanion (it
stays –ate, or –ite.)
USE TABLE 7-2!!!
Al+3 bonding with
(SO3)-2
Gives you
Al2(SO3)3 called
Aluminum Sulfate
• Write the formula for: (use p. 210)
• copper (II) sulfate
CuSO4
• potassium sulfide
K2S
• potassium perchlorate
KClO4
• lithium nitrate
LiNO3
• calcium nitrite
Ca(NO2)2
EXAMPLE: Compounds with polyatomic ions
Give the names for: (use page 210)
• Ca(OH)2
calcium hydroxide
• FeCrO4
iron(II) chromate
• KClO3
potassium chlorate
• NH4OH
ammonium hydroxide
• KClO
potassium hypochlorite
EXAMPLE: Compounds with polyatomic ions
• barium fluoride
• cadmium oxide
• tin(IV) sulfate
• iron(III) nitrate
• sodium hydroxide
•
Warm-Up
• Ag2S
• NH4NO3
• Cu2+
• Fe2+
• Fe3+
• O2• Br-
Most Polyatomic Ions
 Are oxyanions,
polyatomic anions that
contain oxygen.
 Some may form
different ions that
contain the same
elements. The most
common is given the
suffix –ate, the other
ends in –ite.
NO2−
Nitrite
NO3−
Nitrate
If More Than 2 Oxyanions Can Exist
The anion with one less oxygen than the –ite
anion is given the prefix hypo-. An anion with
one more oxygen than the –ate anion is given
the prefix per-.
ClO−
ClO2−
ClO3−
ClO4−
Hypochlorite Chlorite Chlorate Perchlorate
http://antoine.frostburg.edu/chem/senese/101/co
mpounds/polyatomic.shtml
Naming Binary Molecular Compounds
 Molecular
compounds are
covalently bonded
units. Can be
named in two
ways:
Prefix System
 The older system of
nomenclature based on
the use of prefixes to
denote the number of
atoms, or sometimes
the number of groups
of atoms, in a
molecule.
 See Table 7-3, p. 212.
Rules For the Prefix System
 1. The less
electronegative
element is given
first. It is given a
prefix only if it
contributes more
than one atom to a
molecule.
2. The second element is named by
combining
 a. a prefix indicating
the number of atoms
contributed by the
element,
 b. the root of the
name of the second
element, and
 c. The ending –ide.
3. The o or a at the end of a prefix
 Usually dropped
when the word
following the
prefix begins with
another vowel
(monoxide,
pentoxide, etc.)
Thou shalt keep thy
big mouth shut.
• Name the following:
• SO3
sulfur trioxide
• ICl3
iodine trichloride
• PBr5
phosphorus pentabromide
EXAMPLES: Binary Molecular Compounds
• Write the formulas for:
• carbon tetraiodide
• dinitrogen trioxide
• phosphorus trichloride
CI4
N2O3
PCl3
EXAMPLES: Binary Molecular Compounds
Stock System
 Much like the Stock
system for ionic
compounds, but here
we use oxidation
numbers, which is
Section 7-2. We’ll
do this later.
Acids (More on this in Chap. 15)
 Originally recognized as
compounds based on their
properties in solutions of
water (aqueous solutions).
 We usually refer to
solutions in water of these
compounds rather than to
the pure compound itself.
Most Acids Used in the Laboratory
 Can be
classified
into two
main types:
 Also see
Table 7-5, p.
214.
Binary Acids
 Consist of 2 elements,
usually hydrogen and one
of the halogens:
 HF: Hydrofluoric acid
HCl: Hydrochloric acid
In general, if the anion ends
in –ide, the acid name
will end in –ic and begin
with the prefix hydro-.
• Write the name for:
• HI
• HF
• HBr
• HCl
hydriodic acid
hydrofluoric acid
hydrobromic acid
hyrdrochloric acid
EXAMPLE: Binary Acids
Oxyacids
Sulfuric acid – H2SO4
 Acids that contain
hydrogen, oxygen, and a
third element (usually a
nonmetal).
 If the anion ends in -ate
the acid name will end
as -ic. If the anion ends
in -ite the acid will end
as -ous.
• Write formulas for the following
compounds
• Chloric acid
HClO3
• Sulfurous acid H2SO3
• Sulfuric acid
H2SO4
• Phosphoric acid H3PO4
EXAMPLE: Oxyacids
Many Polyatomic Ions
 Are produced by the loss of hydrogen ions (H+)
from oxyacids:
Sulfuric acid
H2SO4
Sulfate
SO42−
Salt
 An ionic compound
composed of a cation and
the anion from an acid.
The old definition was
the product of an acid and
a base reacting to form a
salt and water:
HCl + NaOH → NaCl + H2O
Some Salt Anions Retain H From The Acid
Best example comes from
carbonic acid, H2CO3:
The anion is named by
adding the word
hydrogen or the prefix
bi- to the anion name:
HCO3−
Hydrogen carbonate ion
Bicarbonate ion
A Salt Formed From This
NaHCO3
Sodium bicarbonate
(baking soda)
• IF YOU HAVE A METAL IN
YOUR COMPOUND, YOU
WILL NEVER USE
PREFIXES…ANYWHERE…
EVER
Reminder
Binary MOLECULAR COMPOUNDS using Prefix system
Molecular
Compounds
Definition
Steps in Creating
the Formula
How Do You Name It?
Example
Molecular
Compounds
are covalently
bonded units.
You will usually be
given the formula
and then you can
find the oxidation
numbers of the rest
of the atoms from
there, but you would
normally draw the
Lewis structure
Two ways:
1. The naming system
is for compounds of
two nonmetallic
elements.
2. The first element
gets a prefix if it has
a subscript in the
formula
3. The second element
gets the –ide suffix
(ending)
4. The second element
ALWAYS gets a
prefix.
Ex. CCl4
Carbon
Tetrachloride
Ex. P5O2
PentaPhosphorus
Dioxide
Binary Acids
Binary
Acids
Definition
Steps in Creating the
Formula
How Do You Name It?
Example
Consist of 2
elements,
usually
hydrogen
and one of
the halogens
Will always
have one
hydrogen
bonded to a
highly
electronegative
atom to form
HYDRO-root of
element-IC ACID
Ex. HCl
Hydrochloric
Acid
Oxyacids
OXYACIDS
Acids that
contain
hydrogen and
a polyatomic
ion (the
polyatomic ion
is what has
oxygen in it…)
Steps in Creating the
Formula
How Do You Name It?
Example
Will always have
one hydrogen
bonded to a
negatively
charged group-likely a
polyatomic ion
(ex. NO3-1)
If the anion ends in
-ate the acid name
will end as -ic. If
the anion ends in ite the acid will end
as -ous.
Sulfuric
acid
H2SO4
Sulfurous
acid
H2SO3
SALTS
SALTS
Definition
Steps in Creating the
Formula
How Do You Name It?
Example
An ionic
compound
composed of
a cation and
the anion
from an acid.
The old
definition was
the product of
an acid and a
base reacting to
form a salt and
water:
HCl + NaOH →
NaCl + H2O
The anion is
named by adding
the word hydrogen
or the prefix bi- to
the anion name:
HCO3−
Hydrogen
carbonate ion
Bicarbonate ion
Ex. NaHCO3
Sodium
bicarbonate
(baking
soda)