3.1 Ionic and Molecular Compounds
Saturday, September 03, 2011
10:21 AM
Terms for this section:
Electrolyte
Nonelectrolyte
Strong Electrolyte
Weak Electrolyte
Ionic Compound (salt)
Molecular Compound
Binary Compounds
Ionization/Disassociation
Which of the following are ionic compounds?
A.
B.
C.
D.
E.
KCl
NaOH
CH4
CO2
CaO
Disassociation reaction:
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Properties of Ionic vs. Molecular Compounds
Ionic Compound
Molecular Compound
Crystalline solid
Solid, Liquid, or Gas
Hard, brittle solid
Soft Solid
Very High Melting Point
Low Melting Point
Very High Boiling Point
Low Boiling Point
High Density
Low Density
Strong Electrolyte
Weak or Nonelectrolyte
Conductivity in molten form Poor conductivity
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3.2 Monatomic and Polyatomic Ions
Saturday, September 03, 2011
10:24 AM
Terms in this Section:
Monatomic Ion
Polyatomic ion
Oxoanion
Common Monatomic
Ions:
-Oxide
-Sodium
-Nitride
-Aluminum
-Magnesium
-Chloride
Polyatomic Ions and Oxoanions
-Potassium
Polyatomic ions are ions that contain more than a single
atom, the most common are the Oxoanions which contain
oxygen bound to other elements.
-Flouride
Naming Oxoanions
Single Oxoanion - ends in -ate (such as Borate)
Two Ions and Oxoanions in sequence
No Oxygen - ends in -ide (such as Chloride)
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Two Ions and Oxoanions in sequence
No Oxygen - ends in -ide (such as Chloride)
Most Numbers of Oxygen - ends in -ate
Three Ions and Oxoanions in sequence
No Oxygens - ends in -ide
Middle Numbers of Oxygen - ends in -ite (such as
Sulfite)
Most Numbers of Oxygen - ends in -ate
Some compounds have a total of five in the sequence.
No Oxygens - ends in -ide
Most Oxygens - prefix of per- and suffix of -ate
Next Most - ends in -ate
Next to Least - ends in -ite
Least Oxygens - prefix of hypo- and suffix of -ite
Learn the common Polyatomic Ions in Table 3.4!
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3.3 Formulas for Ionic Compounds
Saturday, September 03, 2011
10:24 AM
Formula Unit vs. Chemical Formula
Ionic Compounds do not exist as discrete molecules and therefore do not have
discrete chemical formulas. You must report the smallest unit value of the
crystal lattice that balances to a net charge of zero.
Problems:
Write the formula for the followingA. Calcium perchlorate
B. Sodium bromide
C. Lithium hypochlorite
D. Potassium Cyanide
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3.4 Naming Ionic Compounds
Saturday, September 03, 2011
10:24 AM
The names of ionic compounds are usually the metal
followed by the
nonmetal name. In the case of polyatomic ions, you
use the
appropriate name for the form present.
NaO = Sodium Oxide
NaCl = Sodium Chloride
Li3PO4 = Lithium Phosphate
Mg(ClO)2 = Magnesium Hypochlorite
Note you do not need to denote the number of
each atom present
in the formula unit, since it can be deduced from
the type of ion.
Try the following:
A. Ca(NO3)2 =
___________________________________________________________
B. K2O =
___________________________________________________________
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C. LiN =
___________________________________________________________
D. Rb4SiO4 =
___________________________________________________________
It isn't always so nice and neat, once you get into the
transition metals
and the metals of Groups IIIA-VIA, many of these
exhibit multiple
charge states and therefore can have multiple formula
units.
For example, there is both a CuCl and CuCl2…
How can this be, this would mean that sometimes
Copper is a +1
cation and sometimes it is a +2 cation… exactly.
We have to have a way to distinguish between these
two types of
compounds. There are a few ways to do this. The
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compounds. There are a few ways to do this. The
preferred way is
simply to designate the charge in the name with roman
numerals.
Such as…
CuCl = Copper (I) Chloride
CuCl2 = Copper (II) Chloride
There is another way, an older but still used
methodology, where the
lower charge ends the metal is -ous and the higher
charge ends the
metal in -ic. Therefore you would get…
CuCl = Copper (I) Chloride = Cuprous Chloride
CuCl2 = Copper (II) Chloride = Cupric Chloride
This gets even weirder because the names of the
metals don't always
match the element.
FeCl2 = Iron (II) Chloride = Ferrous Chloride
FeCl3 = Iron (III) Chloride = Ferric Chloride
SnO = Tin (II) Oxide = Stannous Oxide
PROBLEMS
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A. CrO =
___________________________________________________________
B. Co(NO2)3 =
__________________________________________________________
C. (Hg2)3(PO4)2 =
___________________________________________________________
I advise sticking to the numbering system since it is
valid and
easier to make sense of. The other system is used
and you should
be aware of it, but is outdated.
Know Figure 3.24
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3.5 Naming and Writing Formulas for Molecular Compounds
Saturday, September 03, 2011
10:24 AM
The names of molecular compounds differ because there are a
finite number of atoms present in a molecule (in contrast to the
simplest ratio of ionic compounds). Therefore we need to
explicitly state the number of atoms for each element present.
This is done as follows for binary molecular compounds.
1. The name starts with the element that is first in the molecular
formula.
2. If there is more than one of that element present a Greek
prefix (Table 3.9) is added to denote the number.
3. The second element is added as a root with the suffix -ide
and if there is more than one, an appropriate Greek prefix of
magnitude.
CCl4 = Carbon Tetrachloride
SO3 = Sulfur Trioxide (not to be confused with SO3-2)
Name the Following:
1. P4O6 =
____________________________________________________________________
____
2. N2O5 =
____________________________________________________________________
____
There are trivial exceptions such as water, ammonia and
hydrogen peroxide, but you should strive to systematic.
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3.6 Acids and Bases
Saturday, September 03, 2011
10:25 AM
Acid = Any substance that provides hydrogen ions (H+) when
dissolved in water. These are typically molecular compounds
that ionize, a type of disassociation, in water. The following is a
typical ionization reaction. This differs from the breakdown of
an ionic compound because the process is not complete, rather
on part of the substance ionizes (which we will learn about in
equilibria)
HCl(g) + H2O(l) ----> H3O+(aq) + Cl-(aq)
So what is H3O+…
This is the hydronium ion and represents the association of the
freed hydrogen ion with water.
Acids are typically produced between hydrogen and element on
the right of the periodic table (halogens being notable), though
there are exceptions to this.
Work through tables 3.10 and 3.11 to see if you can work out
the naming rules for binary acids.
Base = any compound that dissolved in water reacts with an acid
to form water. This may be through the release of OH-, or
through the production of OH-.
NaOH
NH3
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Review Problems
Saturday, September 03, 2011
10:26 AM
Try to do the following, without your notes or book at first. These types of
problems will be on the exam.
Given the following formulas, please name the compounds.
1. Na3As : ___________________________________________________________
2. MgO : _____________________________________________________________
3. Ba3(BO3)2 : ________________________________________________________
4. NH4Cl : ____________________________________________________________
5. K2Cr2O7 : __________________________________________________________
Write the formula units for the following compounds
1. Barium Phosphate: _______________________________________________
2. Iron (III) Chloride: _________________________________________________
3. Lithium Nitride: ___________________________________________________
4.
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