Section 2.6: Molecular and
Ionic Compounds
By
Doba Jackson, Ph.D.
Molecules, Ions, and Chemical
Bonds
Covalent Bond: A bond that results from the
sharing of electrons between atoms.
Ionic Bond: A bond that results from oppositely
charged ions that are electrostaticlly attracted to
each other.
Definitions of Molecules, Ions,
and Chemical Bonds
Ionic Bond: An electrostatic attraction between
charged particles. Typically a metal bonded to a
nonmetal.
Ion: A charged atom or molecule.
Cation: A positively charged particle. Most cations
are metals.
Anion: A negatively charged particle. Nonmetals tend
to form anions.
Ions, and Chemical Bonds
In the formation of sodium chloride, one electron is
transferred from the sodium atom to a chlorine
atom.
11 protons 17 protons
11 electrons 17 electrons
Na
+
1
2
Cl2
Na+1
11 protons
10 electrons
+
Cl-1
17 protons
18 electrons
Evidence for existence of ions
We can predict many element’s ionic
charge based on its location on the
periodic table
Naming Ionic Compounds
+1
Naming (IUPAC)
+2
Cation Anion
Na+1
Cl-1
Sodium Chloride
Metals tend to form Cations
Nonmetals tend to form Anions
+3
-3 -2 -1
Naming Ionic Compounds
Ionic Compound: A neutral compound in which the
total number of positive charges must equal the total
number of negative charges.
Some binary Ionic Compounds
Cation – Anion(ide)
Cation
Anion
Ionic
Compound
sodium chloride
Na+1
Cl-1
NaCl
magnesium oxide
Mg+2
O-2
MgO
aluminum sulfide:
Al+3
S-2
Al2S3
cation anion(ide)
+x
C
-y
A
CyAx
Determine the charge on each ionic
compound and name the compound
MgS
Mg+2
S-2
Magnesium sulfide
BaF2
Ba+2
F-1
Barium flouride
AlP
Al+3
P-3
Ga2O3
Ga+3
Li2O
Mg3N2
Li+1
Mg+2
O-2
O-2
CaS
Ca+2
S-2
Calcium sulfide
Fe2O3
Fe+3
O-2
Iron (III) oxide
PbO2
Pb+4
O-2
Lead (IV) oxide
NiBr2
Ni+2
Br-1
Nickel Bromide
MnO2
Mn+4
WBr6
W+6
O-2
Br-1
N-3
Aluminum Phosphide
Gallium oxide
Lithium oxide
Magnesium nitride
Manganese (IV) Oxide
Tungsten (VI) bromide
Some transition metals have more than one stable charge
What happens when the cation has
more than one oxidation state
Use Roman numerals in parentheses to indicate the
charge on metals that form more than one kind of
cation.
Some binary Ionic Compounds
Ionic
Compound
Cation Anion(ide)
Cation
Anion
iron (III) oxide
Fe+3
O-2
Fe2O3
tin (II) chloride
Sn+2
Cl-1
SnCl2
lead (II) flouride
Pb+2
F-1
PbF2
cation (x) anion(ide)
C
+x
A
-y
CyAx
Molecules, Ions, and Chemical
Bonds
Covalent Bond: A bond that results from the
sharing of electrons between atoms.
Ionic Bond: A bond that results from oppositely
charged ions that are electrostaticlly attracted to
each other.
Definitions of Ionic and Covalent
compounds
• Ionic bonds are a result of a combination of a
metal (electropositive element) and a nonmetal (electronegative element).
• In ionic bonds, atoms are attracted to each
other by opposite charges.
• Covalent bonds are a result of the combination
of two non-metals (two electronegative
elements).
• In covalent bonds, atoms are attracted to each
other by a shared pair of electrons.
A Comparison of Ionic and
Covalent Bonds
Points to consider: Ionic
verses Covalent compounds
Point 1: Ionic compounds are
usually solids (when pure)
Point 2: Ionic compounds
have very high boiling and
melting points
Point 3: Covalent compounds
can be either solids, liquids
or gases
Point 4: Covalent compounds
have relatively lower boiling
and melting points
Why does NaCl have such high
boiling and melting points?
A chemical representation of a
covalent compound (ethanol)
Predict whether each compound is
an ionic or molecular compound.
• KI,
component in table salt
Ionic: 1 metal
1 nonmetal
• H2O2, antioxidant
Molecular: 2 nonmetals
• CHCl3, anesthetic
Molecular: 3 nonmetals
• Li2CO3, antidepressants
Ionic: 1 metal
2 nonmetals
To name nonmetals, we first have to
understand a concept called Electronegativity
Electronegativity: The ability of an atom in
a molecule to attract the shared electrons
in a covalent bond.
Naming Covalent Compounds:
Must know these prefixes
Choose which compound is more
electronegative, then change the suffix to -ide
- Write the name: electropositive - electronegative
- Add the suffix “ide”
electronegative atom.
to
the
end
of
the
- Use the prefixes to indicate the multiplicity of the
both atoms.
Example: naming N2O4
N2O4
The first element
(Nitrogen) is more
electropositive and
takes the name of the
element.
The second element
(Oxygen) is more
electronegative and takes the
name of the element with an
“ide” modification to the
ending.
The prefix is added to the front of each to
indicate the number of each atom.
dinitrogen tetraoxide
WORKED EXAMPLE
Give systematic names for the following
compounds
Solution
(a) PCl3
Phosphorus trichloride
(b) N2O3
Dinitrogen trioxide
(c) P4O7
Tetraphosphorus heptoxide
(d) BrF3
Bromine trifluoride