Prescriptive Activities: Facet Cluster 2.2: PF#81
Teacher Page
Prescriptive #81:
81 The student thinks that whether or not a substance can conduct an electrical current or
is a good conductor of heat is a result of a lot of electrons in the valence orbitals.
Materials:
Student handout
Sea of mobile electrons in a metal1
Background:
Copper is used to make wires because it is one of the best
electrical conductors. Copper has two valence electrons. In
the diagram shown here, the “mobile sea of electrons”,
indicated by little dots with “-“ next to them, consists of
these two electrons from each copper atom, which are free to
flow between the cations in the metal lattice. Note that this is
a simplified representation of what we think is actually
happening in a conductive metal based on observation and
experimentation.
Questions:
1. A list of the 4 most electrically conductive metals is shown at the
right in order of decreasing conductivity. How many valence
electrons does aluminum have?
2. Based on this list, do you think there is a direct relationship
between the number of valence electrons and the conductivity of
a metal? Explain.
3. A few other metals which are less conductive than aluminum are
shown at right, in order of decreasing conductivity. Does this list
support your answer to the previous question? Explain.
4. Why do you think copper is used for wiring instead of silver
even though silver is a better electrical conductor?
1
Metal
Silver
Copper
Gold
Aluminum
Metal
Sodium
Tin
Strontium
Gallium
http://www.daviddarling.info/encyclopedia/M/metallic_bond.html
# of valence
electrons
1
2
1
# of
valence
electrons
1
4
2
3