Now to understand WHY Copper, Silver and Gold are the best for Conductivity is to understand the atomic structure of Atoms. You have a center core of Protons and Neutrons, with the electrons revolving around the center core. Like the Planets going around the Sun, the electrons are in “orbits” around the center core, but unlike the Plants, the electrons often have more than one electrons in an orbit.
Now each orbit has a set number of electrons to make it “full”. In the First Orbit that number is 2 electrons, in the Second Orbit it is 8 electrons, in the third it is 18 electrons, in the Fourth it is 18 electrons (and than 32 after the Fifth orbit has reached 18).
Electricity conducts best when the OUTERMOST ring of electrons has only 1 electron AND The rest of the rings are full. This occurs in column 1b of the Periodic table. Three natural occurring elements exists in that column, Copper, Silver, and Gold.
Thus these three elements are the preferred elements for transporting electric current, and why all are used in electric circuitry.
For a Periodic Chart:
http://education.yahoo.com/reference/encyclopedia/entry?id=36717Copper
Symbol: Cu
Atomic Weight: 63.546
2 8 18 1
Atomic Number: 29
Silver
Atomic Number 47
Symbol Ag
Atomic Weight 107.8682
2 8 18 18 1
Gold
Symbol Au
Atomic Number 79
Atomic Weight 196.9665
2 8 18 32 18 1