Page 415 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

Some Aspects of the Chemistry of Copper and Bronze

A P P E N D I X A

COPPER
Copper is a salmon pink or reddish element with a bright metallic luster. It is malleable, ductile,
and a good conductor of heat and electricity, which is one of the principal reasons for its exten­
sive use today. Like silver and gold, copper is a face-centered cubic metal. Its most important
alloys are with arsenic, tin, antimony, and zinc, and these alloys often have added lead.
Large deposits of copper are now found in the United States, Chile, Zambia, Zaire, Peru,
and Canada (Weast 1984). None of these locations were particularly important in ancient times
with the exception of Peru, which was to become important during the Moche period in the
early centuries C.E. for its copper-arsenic ores. In other parts of the world, small deposits of oxi­
dized copper ores must have been much more widespread than they are now. These deposits are
unknown to modern commercial copper mining either because they are too small or insignifi­
cant or because most of the copper minerals have already been exhausted from these locations.

Electronic configuration Copper has a single s electron outside of a completed d shell.
The filled d shell of copper is much less effective than that of a
noble gas in shielding the s electron from the nuclear charge, so the first ionization potential of
copper is higher than in the alkalies. The electrons of the d shell are involved in bonding, so the
heat of sublimation and the melting point of copper are also much higher than the alkalies. Not
only are these factors responsible for the more noble character of copper, but they also make
copper compounds more covalent. The second and third ionization potentials of copper are
much lower than those of the alkalies; they are also partly responsible for the transition metal
nature of copper, which is characterized by colored paramagnetic ions and many complexes in