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!

All About Alloys

There are some familiar metals that are actually mixtures of several different types of metals - they are called alloys (AL-oise). Here are a few you've probably heard of (and some that are likely new to you):

• Steel: mixture of iron and one or more other metals (there will be a separate post about steel later)
• Brass (copper and zinc): a shiny yellow metal that looks a little like gold
• Bronze (copper and tin): a dark gold to brown metal that gets darker in color as it ages
• Pewter (copper, tin, and lead): a dark gray metal used for bowls, flatware, jewelry and other decorative items
• Solder (lead and usually tin): an alloy that melts at a relatively low temperature; used to make electrical circuits
• Nitinol (nickel and titanium): this alloy remembers its original shape; used to make eyeglass frames
• Electrum (gold and silver): also known as white gold; used in jewelry
• Alnico (aluminum, nickel, and copper): used to make magnets
• Amalgam (silver, tin, copper, zinc, and mercury): a soft alloy that has been used to fill dental cavities
• Nichrome (nickel and chromium): an alloy that glows orange-red and gives off heat when an electrical current is passed through it; used in toasters and electric burners

Take a look around your house and see how many examples of alloys you can find!

Fun Facts 5

Sometimes it just seems like the fun will never end! But actually, we're not even half done talking about the elements!

• Most plants are green because they contain chlorophyll, which lets them turn light into energy. Chlorophyll is a large and complex molecule, but at its heart is a magnesium (Mg, #12) atom.
• Scandium (Sc, #21) is a lightweight metal that is sometimes combined with aluminum to make sports equipment, like bikes and baseball bats.
• Marguerite Perey, a student of the famous woman scientist Marie Curie, discovered francium (Fr, #87) in 1939. It was the last naturally occuring element to be discovered.
• The element californium (Cf, #98) has been detected in supernovas, which are exploding stars.
• Gold (Au, #79) is sometimes used to make false teeth. In fact, some skeletons from the Etruscans, who lived in Italy in 1000 - 400 BCE, had good teeth!
• Only about 100 atoms of the very radioactive element hassium (Hs, #108) have ever been made!
• Lithium (Li, #3) batteries are small, lightweight, and long-lasting. Some of them can supply power for over 10 years!
• Some who is famous is sometimes said to be "in the limelight". This phrase doesn't refer to green fruits at all, but rather, to calcium (Ca, #20) oxide, also called "lime". In the early 1800's (before electric lights), lime was burned with oxygen and hydrogen to produce a very bright white light. This light was usually used to illuminate stages in theaters and concert halls.
• The silvery metal gallium (Ga, #31) has a melting point near body temperature. This means that it will melt in your hand if you hold it!
• One element was so hard to discover that its name comes from the Greek word dysprositos, which means "hard to get at". That element is dysprosium (Dy, #66).