MAN AND METAL

MAN AND METAL

We are surrounded by a cacophony of metals. Aluminum cans store sweet, caffeine-filled beverages that give an afternoon boost. Iron support structures weave throughout every modern building, and our pockets jingle with nickel and copper coins. The rare metals gold and platinum may be a little less common in our day-to-day lives, but they play important roles in electronics, internal combustion engines, and, of course, jewelry. In the past three decades, industrial needs have led to the use of a number of lesser known, rare metals to advance consumer electronics, health care, communications, and the defense industry.

These "new" metals are often fugitives from the bottom rows of the periodic table—metals with names like niobium, tantalum, and rhodium. These elements were likely overlooked in your high school or college chemistry class, but they play a litany of roles in the technological growth of society, as engineers, chemists, and physicists push the boundaries of the exciting and possible.

Humankind's past is littered with methods of using metals to fashion weapons and tools, with the earliest notations appearing six thousand years ago. While metals may vary in scarcity, this brotherhood shares a number of basic characteristics: they are overwhelmingly malleable and act as superb-quality conductors of electrons, for example. Our word metal derives from the Greek word metallon. The word loosely translates to "quarry" or "mine" and was often used in reference to bustling gold- and silver mining operations in ancient Greece. This is quite the adequate name, one defined by its source, with metals often requiring a phenomenal amount of work to pry from Earth's grip.

Scientifically, metals are known for a common set of properties. Almost all metals have the ability to transmit electricity and heat—very useful properties in the world of electronics. Most metals can be easily bent and molded into intricate shapes. As a nice bonus, most metals are resistant to all but the most extreme chemical reactions in the outside environment, with the added stability increasing their usefulness. A very apparent exception to this stability, however, is the rusting of iron, a natural process that occurs as iron is exposed to oxygen and water over time in junkyards, barns, and elsewhere.

Is a particular metal hard to find because there is a limited amount, is it simply difficult to retrieve, or does technological demand outpace supply? The acquisition difficulty is likely due to a combination of all these reasons with a dash of nostalgic value to top things off for good measure, particularly for rare metals like gold and platinum that have served as status symbols for thousands of years.

ONE IN A BILLION

Determining a definitive amount of an individual element is a tricky endeavor. If you dive into a physics textbook, you are greeted with estimates of percentage makeup of the universe, solar system, and galaxy by element. If humankind has yet to set foot on Mars, how do we have any idea what percentage of elements make up other galaxies? These estimates are made through a combination of techniques and theories taken from physics, chemistry, and astronomy, relying on high-tech instrumentation to obtain data—after all, several-hundred-million-dollar telescopes are not just for pretty pictures. By looking for fluctuations in the way light bounces back based on what is known regarding how individual atoms of a given element reflect light, rudimentary abundance estimates are made.

Measuring the amount of a given metal on Earth is bit easier but is still an astounding feat. The abundance of metals within the planet's crust is often reported in arcane "parts per" notation. These parts-per-million (and often parts-per-billion) values are attained through painstaking analysis of large amounts of rocks taken from the earth's crust. Ideally, they represent an average amount should all the metals be uniformly distributed throughout the planet—which, as we know, they are not.

Parts per million (or billion), when used without any context, is a horribly obscure measurement that plagued my afternoons spent in Analytical Chemistry Lab. A notation traditionally used to communicate the amount of a contaminant within water or air, parts per million takes a very tiny amount and casts it against a reasonable background. Due to its nature, "parts per" is a dimensionless measurement—it lacks units. These measurements describe a quantity, but not in relation to a known commodity as measurements like fifty miles per hour, ten feet, or one hundred kilometers do.

Thanks to its analytical anonymity, a "parts per" measurement can be used to describe just about anything. By the time you finish the end of this sentence, you have used about two parts per billion of your life—about four and a half seconds of the average human life-span. This sort of measurement is a great way to obscure the facts—a local newscast might state there are three parts per billion of a toxic chemical like lead in the water supply. This is also the way the amount of rare earth metals is often reported. For example, platinum, a scarce, precious metal, exists in four parts per billion of Earth's crust—only four out of a billion atoms within the crust are platinum. This is an extremely small amount. To put the amount of platinum on Earth in an easier-to-visualize light, imagine if one took all the platinum mined in the past several decades and melted it down; the amount of molten platinum would barely fill the average home swimming pool.

Silver, a metal many use on a daily basis to eat with, exists at only a twenty-parts-per-billion value—twenty out of every billion atoms on the planet are silver. Remind your significant other of that fact the next time you go jewelry shopping, and you might save some cash. Osmium, rhenium, iridium, ruthenium, and even gold exist in smaller quantities, much less than one part per billion, while some are available in such small concentrations that no valid measurement exists.

On the extreme end of the scarcity spectrum is the metal promethium. The metal is named for the Greek Titan Prometheus, a mythological trickster who is known for stealing fire from the gods. Scientists first isolated promethium in 1963 after decades of speculation about the metal. Promethium is one of the rarest elements on Earth and would be very useful if available in substantial amounts. If enough existed on the planet, promethium could be used to...