Lab 5.4
Ionic vs Covalent Compounds
Conductivity
• For a substance to conduct it
must have:
1. Particles that are free to
move
2. Charged Particles
Conductivity of Solutions
Salt vs. Sugar
The particles
must be charged.
The particles
must be neutral
(not charged).
Salt and Sugar both dissolve in water, forming clear solutions.
During dissolving, the particles of the solid salt or sugar became
free to move. So, while both have met that requirement of
conductivity, only salt meets the 2nd requirement.
Solutions that Conducted
Name
Formula
Sodium chloride
(salt)
Potassium
bromide
Magnesium
sulfide
Barium iodide
NaCl
Combination of
Elements
M-nm
KBr
M-nm
MgS
M-nm
BaI2
M-nm
Solutions that Conduct
• Ionic Compounds:
– Composed of metal and nonmetal elements
– Composed of charged particles called ions
• Ion = an atom that has become charged
Positive
Ion
Negative
Ion
Ionic bond: attraction
between the oppositely
charged ions
In the solid salt, there
are charged particlesthe ions, but they are
not free to move
Dissolving
Ions are free to move
in the salt solution
Dissolving an Ionic Compound
• Watch the following animation:
Dissolving an ionic compound
Dissolving an ionic compound #2
+
-
+
+
+
The ionic bond that
once held the
oppositely charged ions
together is now broken.
-
-
+
-
Water particles are not
shown. Each ion is
surrounded by many water
particles, keeping them
separate and no longer
attracted to each other.
Naming Ionic Compounds
• Metal name goes 1st with no change.
• Nonmetal name is changed to an “-ide”
ending.
• Sodium chloride, NOT sodium chlorine
• Aluminum oxide, NOT aluminum oxygen
Solutions that Don’t Conduct
Name
C12H22O11
Combination of
Elements
Nm-nm
Ammonia
NH3
Nm-nm
Isopropynl
C3H8O
Nm-nm
CO2
Nm-nm
Sugar
Carbon dioxide
Formula
Solutions that do NOT conduct
• Covalent Compounds:
– Composed of only nonmetal elements.
– Composed of neutral particles called
molecules.
• Molecule = group of atoms bonded together that
acts as a single unit (particle)
Molecules
Each individual
molecule is “intact”;
the atoms are still
bonded as a group.
The covalent bond
between the nm
atoms has not been
broken.
Naming Covalent Compounds
• Element listed first in the formula is named
first with no change.
• 2nd element is changed to “-ide” ending
AND is preceded by a prefix.
• Carbon dioxide, NOT carbon oxide.
• Carbon tetrachloride, NOT carbon
chloride.
Molecular Nomenclature Prefixes
PREFIX
monoditritetrapentahexaheptaoctanonadeca-
NUMBER
1
2
3
4
5
6
7
8
9
10