Copper, an ignoble metal

August 18, 2010

Seriously. Copper is totally not noble. Gold and silver. Those are some noble metals. Copper corrodes. You’ve all seen what happens to bronze (~ 88% copper and 12% tin) statues. They turn green. They tarnish. They start off beautiful and, well, bronze. But, they just can’t stand the oxygen in the air. It diminishes them.

Pamona, the goddess of plenty.

Copper can also be a very toxic and damaging material. For a long time, the semiconductor industry feared copper, small amounts of which would destroy their microchips during the fabrication process. High doses of copper in its +2 ionic state (or cupric state) can be lethal to humans. Wilson’s disease, a genetic disorder that leads to the accumulation of copper in tissues, presents itself, initially, as tiredness or confusion. Ultimately, this disease can have much more visual effects on the human body, as seen below.

Deposits of copper in the cornea, known as a Kayser-Fleischer ring.

Despite all of these shortcomings, copper is a beautiful element that our lives are very dependent upon. In human history, we have had both a Copper and a Bronze Age in our technical evolution. Copper has truly made us what we are today.

Natural copper deposit.

Because of its electronic structure (with a sole electron hanging out in its 4s orbital – for those aficionados out there) copper, like silver and gold, is an excellent conductor of electricity. Nearly all of the electric circuits in our fancy appliances are made of copper. (I just bought a HDMI cable the other day that has gold-plated copper in it).

Our bodies are in constant need of copper, despite its toxicity. Superoxide dismutase (a protein enzyme which acts as an antioxidant) and cytochrome c oxidase (a protein that turns oxygen in to water and energy) both need copper to work properly. Just like in your fancy TV, your body also relies on copper proteins (like the strikingly beautiful azurin and plastocyanin) to carry electrons from one place to another.

The blue color comes from the protein azurin, which is being purified in this photo. Credit: Kyle M. Lancaster

So, let’s give three cheers to copper, cuprous and Cupric! This is not-so-precious, most ignoble metal without which our lives would be very much different and not nearly as interesting!