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 Sea of mobile electrons in a metal1
in the valence orbitals. Materials:
Student handout
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.
Metal
Silver
Copper
Gold
Aluminum
# of valence
electrons
1
2
1
Metal
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 Sodium
Tin
Strontium
Gallium
http://www.daviddarling.info/encyclopedia/M/metallic_bond.html # of
valence
electrons
1
4
2
3