Precious!

Not all metals oxidize, tarnish, or otherwise form coatings when exposed to air. With the exception of silver, the so-called precious metals - gold, platinum, iridium, palladium, rhodium, ruthenium, rhenium, and osmium - do not react with chemicals in the air, and remain shiny and beautiful. Because of this, they are often used to make jewelry.

And these metals really are precious! Here are some typical prices for one ounce of some precious metals as of July 2011: $40 for silver (not too bad!), $800 for palladium, $1600 for gold, $1800 for platinum, and a whopping $4500 for rhenium!

The funny thing is that one metal used to be precious, but isn't any more, and that's regular old aluminum. We now make disposable cans and food containers out of aluminum (although it's always good to recycle when possible), but at one time, aluminum was more expensive than gold! In fact, in the early 1800's, the French emperor Napoleon had special flatware (forks, spoons, and knives) made out of aluminum, which he used for only his most important dinner guests. Why was aluminum so expensive? Unlike many other metals, aluminum does not occur naturally in pure metallic form. Much of is was found as alum, a mineral from which the aluminum must be separated. In Napoleon's time, this was a very long and difficult process. But in the late 1800's, an American chemist named Charles Martin Hall discovered a process that used electricity to obtain aluminum from alum cheaply and easily. Its price fell from $600 per pound in 1850 to 18 cents per pound in 1914. Hall and some partners formed the Aluminum Company of America (now Alcoa). One other interesting note about Hall - he was very young when he discovered his aluminum process. In fact, he had just graduated from college a few years before!

Fun Facts 4

Continuing with our cavalcade of fun facts:

• The skeletons of certain types of sponges and other sea creatures are made up of silicon (Si, #14) dioxide, or SiO2. SiO2 is also the main component of glass, sand, and many rocks.
• Adding molybdenum (Mo, #42) to steel makes the metal even stronger. "Moly steel" was developed in the early 1900's, but a Japanese sword made in 1330 contains a lot of molybdenum. No one know how this was done!
• Bohrium (Bh, #107) is named after the Danish physicist Niels Bohr, whose birthday is today, October 8! Tillykke med fødelsdagen, Niels! (Apologies to any Danish speakers out there if this isn't right). Bohr was the scientist who first thought of the "miniature solar system" picture of the atom. Scientists later realized that this picture wasn't exactly right, but it was still an important idea!
• Osmium (Os, #76) is the densest metal. A one-foot cube of osmium would weigh over 140 pounds - that's heavier than many adults!
• Gadolinium (Gd, #64) is one of the elements called "rare earths" (#57 - #70), but it really isn't terribly rare. In fact, there is more Gd on earth than tin!
• Europeans didn't "discover" the beautiful silvery metal platinum (Pt, #78) until the 1700's. However, the native people of the Americas knew about it long before that!
• If you've ever flown on a plane, you know that the flight attendants tell you about the oxygen (O, #8) masks that drop down from the ceiling in case of a problem. The plane doesn't actually have containers of this gas (that would be dangerous), but they do carry chemicals that make oxygen when they react. If there is a problem, the two chemicals are mixed very quickly, and you can have oxygen gas to breathe!
• People with high blood pressure sometimes use a salt substitute instead of regular salt. This fake salt is actually potassium (K, #19) chloride.
• The metal indium (In, #49) makes a crying sound when a piece of it is bent!
• Radioctive neptunium (Np, #93) is the heaviest element found on earth, but it's only here in very tiny, tiny amounts.