Section 3.0
Compounds Form According to
a Set of Rules
NaCl
C12H22O11
Section 3.1 Naming Compounds
• A compound occurs when two or more elements
combine chemically to produce a new
substance.
• Each compound has its own chemical name
and formula.
• Chemical formula – identifies which elements
and how many of each are in a compound
For example:
• water’s chemical formula is H2O
• water has 2 hydrogen atoms and 1
oxygen.
• The number 2 is a subscript.
Nomenclature:
• In 1787, Guyton de Morveau created a
naming system for chemicals.
• The metallic element name is written first
followed by the non-metallic element.
• Since 1920, the International Union of
Pure and Applied Chemistry or IUPAC
governs the naming of compounds.
• A compound’s physical state at room
temperature is always given in brackets after the
chemical formula:
(g) = gas
CH4 (g)
(l) = liquid
H2O (l)
(s) = solid
NaCl (s)
• For substances that can be dissolved in water,
the subscript (aq) aqueous is used.
Section 3.2 Ionic Compounds
• An ionic compound is a pure substance formed
by attraction between particles of opposite
charges, called ions.
• Ions are simply Atoms that have a charge.
• properties of ionic substances:
–
–
–
–
high melting point
electrical conductivity when dissolved in water
distinct crystal shape
solids at room temperature
• When ionic substances dissolve in water,
the metallic and non-metallic elements
separate to become ions (electrically
charged particles due to the gain or loss of
electrons).
• This allows ionic solutions to conduct
electricity.
Ion charges
• Ion charges are shown by a superscript of either
a plus sign or a minus sign.
Cations (+):
• Positive ions, called cations, have lost electrons
• Metals tend to form cations.
• If 1 electron is lost, the cation has a 1+ charge, if
2 electrons are lost, the cation has a 2+ charge,
and so on.
Anions (-):
• Negative ions, anions, have gained electrons.
Non-metals tend to form anions.
• How do you remember which ions are
positive?
• How do you remember which ions are
positive?
• Just remember, “Cats have Pos”!
• By looking at the periodic table, a pattern in ion charges
can be seen. Generally, all the elements in a group
have the same charge. (See Fig 3.9, p. 147).
Naming Ionic Compounds
• Use the full name of the metal (cation) ion first
• Put the name of the non-metal (anion) last and change
the ending to –ide
• Exception: if the anion is a polyatomic ion, its name
remains unchanged
• If the cation has more than 1 possible charge, indicate
which ion is being used with roman numerals
• eg. iron (III) oxide is a compound containing Fe3+
Name the Following Ionic Compounds:
1.
2.
3.
4.
5.
6.
NaCl (s)
LiBr (s)
CaO (s)
Sr2Cl (s)
BaF2 (s)
K2S (s)
Name the Following Ionic Compounds:
1.
2.
3.
4.
5.
6.
NaCl (s)
LiBr (s)
CaO (s)
Sr2Cl (s)
BaF2 (s)
K2S (s)
sodium chloride
lithium bromide
calcium oxide
strontium chloride
barium fluoride
potassium sulfide
• Polyatomic ions are groups of atoms that
when together have a charge. (Some
examples are on the next slide)
• You will find the polyatomic ions on your
periodic table.
Polyatomic Ions
(these groups of atoms tend to combine together but still have a charge)
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Ammonium
Bicarbonate
Carbonate
Chlorate
Chromate
Dichromate
Hydroxide
Nitrate
Nitrite
Permanganate
Phosphate
Phosphite
Sulphate
Sulphite
NH4+1
HCO3-1
CO3-2
CIO3-1
CrO4-2
Cr2O7-2
OH-1
NO3-1
NO2-1
MnO4-1
PO4-3
PO3-3
SO4-2
SO3-2
Now name these Ionic Compounds:
(these ones contain polyatomic ions)
1.
2.
3.
4.
Li2CO3
KClO2
CaSO4
Ba(NO2)2
Now name these Ionic Compounds:
(these ones contain polyatomic ions)
1.
2.
3.
4.
Li2CO3
KClO2
CaSO4
Ba(NO2)2
lithium carbonate
potassium chlorite
calcium sulfate
barium nitrite
• If the cation can have more than one
possible charge, you must specify which
ion is being used.
Example:
Name Fe2O3
• If the cation can have more than one
possible charge, you must specify which
ion is being used.
Example:
Name Fe2O3
Fe3+ and Fe2+ are both possible ions of iron
• If the cation can have more than one
possible charge, you must specify which
ion is being used.
Example:
Name Fe2O3
Fe3+ and Fe2+ are both possible ions of iron
Fe3+ + O2- = Fe2O3 Iron (III) ioxide
• If the cation can have more than one
possible charge, you must specify which
ion is being used.
Example:
Name Fe2O3
Fe3+ and Fe2+ are both possible ions of iron
Fe3+ + O2- = Fe2O3 Iron (III) ioxide
Fe2+ + O2- = FeO Iron (II) ioxide
• If the cation can have more than one
possible charge, you must specify which
ion is being used.
Example:
Name Fe2O3
Fe3+ and Fe2+ are both possible ions of iron
Fe3+ + O2- = Fe2O3 Iron (III) ioxide
Fe2+ + O2- = FeO Iron (II) ioxide
Name the following compounds:
HgF2
NiBr3
PbS2
Name the following compounds:
HgF2
Hg2+ Hg1+
NiBr3
PbS2
F-
Name the following compounds:
HgF2
mercury (II) fluoride
Hg2+ Hg1+
FNiBr3
PbS2
Name the following compounds:
HgF2
mercury (II) fluoride
Hg2+ Hg1+
FNiBr3
nickel (III) bromide
Ni2+ Ni3+
BrPbS2
Name the following compounds:
HgF2
mercury (II) fluoride
Hg2+ Hg1+
FNiBr3
nickel (III) bromide
Ni2+ Ni3+
BrPbS2
lead (IV) sulfide
Pb2+ Pb4+
S2-
Using Ion Charges and Chemical Names to Write Formulas
• Write the metal element symbol with its charge, next to it
write the non-metal element symbol with its charge
• Balance the ion charges so the net result is a charge of zero
• Write the formula indicating how many atoms of each
element are in it with a subscript.
• If there is only 1 atom of an element, no subscript is needed
For example: barium chloride
Ba2+
Cl-
For example: barium chloride
Ba2+
Cl-
How many of each ion do you need to
balance the charges?
For example: barium chloride
Ba2+
Cl-
How many of each ion do you need to
balance the charges?
Ba2+
ClCl-
For example: barium chloride
Ba2+
Cl-
How many of each ion do you need to
balance the charges?
Ba2+
BaCl2
ClCl-
Write the formulas for the following Ionic Compounds:
1.
2.
3.
4.
5.
Potassium chloride
Calcium chloride
Iridium oxide
Zirconium nitride
Cobalt (II) chloride
Write the formulas for the following Ionic Compounds:
1.
2.
3.
4.
5.
Potassium chloride
Calcium chloride
Iridium oxide
Zirconium nitride
Cobalt (II) chloride
K+ ClCa2+ ClIr4+ O2Zr4+ N3Co2+ Cl1-
KCl (s)
CaCl2 (s)
IrO2 (s)
Zr3N4 (s)
CoCl2 (s)
Section 3.3
Molecular Compounds
• Molecular compounds, or molecules, are formed
when non-metals combine.
• Some properties of molecular compounds are:
- low melting and boiling points (forces between
molecules are weaker)
- poor conductors of electricity, good insulators
- can be solids, liquids or gas at room
temperature
Naming Molecular Compounds
• Many molecules are known by their
common names, such as water, H2O, and
ammonia, NH3. Others are named as
follows:
•
Use the full name of the first element (the most
metal-like goes first)
•
Put the name of the second element last and
change the ending to –ide
•
Use the correct prefix to indicate the number of
each element
•
Exception: do not use the prefix mono when
the first element only has 1 atom
Number of Atoms
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Prefix
mono
di
tri
tetra
penta
hexa
hepta
octa
nona
deca
So:
To name molecules . . .
Prefix + First Element, Prefix + Second Element (with –ide
ending)
Name the following molecular compounds:
1. CO2
2. NO3
3. N2O
4. NF3
5. N2O3
6. CO
Name the following molecular compounds:
1. CO2
carbon dioxide
2. NO3
nitrogen trioxide
3. N2O
dinitrogen monoxide
4. NF3
nitrogen trifluoride
5. N2O3
dinitrogen trioxide
6. CO
carbon monoxide
Remember: The number in subscript tells us
how many of each element are in the
compound.
Comparing Ionic and Molecular Compounds
• Ionic Compounds tend to have high melting and
boiling points are therefore usually solids at
room temp.
• Ionic solutions conduct electricity.
• Molecular compounds tend to have low melting
and boiling points are therefore usually gases or
liquids at room temp.
• Molecular solutions do not conduct electricity