Carbon, hydrogen, nitrogen, oxygen--the famous elements atop the periodic table steal all the headlines. At the far end, in the table's highest numbers, lie unstable elements that only exist for fractions of a second before they radioactively decay. But in between lie the fields of forgotten nuclei: elements with funny names that nonetheless turn up in machines, medicines, and international intrigue.

Praseodymium, Atomic Number: 59

If you've ever welded metal, thank praseodymium that you can still see. Praseodymium is mixed with its periodic next-door neighbor, neodymium, to create didymium glass. The glass is transparent yellow but blocks infrared radiation, so didymium is used in safety goggles for glassblowing and welding masks.

Osmium, an obscure metal, was once the go-to material for phonograph needles, back in the early days of recorded music when 78 RPM discs made of wax were in vogue. Once wax gave way to vinyl records, osmium fell out of favor, and styluses were made from sapphire or diamond.

However, levels of the relatively rare element appear to be rising in the environment--it's produced by the platinum-refining process used to make catalytic converters in cars.

Along with arsenic and mercury, antimony is one of the deadliest elements on the table. But like osmium, this substance is also intertwined with the history of music. For one thing, antimony bears the distinction of being the first element named in Tom Lehrer's "The Elements" song from the 1950s, in which Lehrer sang all the elements of the periodic table to a Gilbert and Sullivan tune.

And, in the grand tradition of horribly misguided medical cure-alls, doctors often prescribed antimony as medicine. One such patient who took it was Wolfgang Amadeus Mozart. The genius composer was treated with antimony for his depression and fever shortly before dying at the age of 35. So might've been chemistry, not Salieri, that did him in.

With an atomic number of four, beryllium feels like the odd one out on this list. But the fourth element gets lost between its more famous single-digit companions like oxygen or helium. NASA often uses beryllium because it's a light metal and non-magnetic, and the element will soon accompany a prestige mission: The James Webb Space Telescope, the Hubble telescope's successor-to-be, will carry 18 mirrors made of beryllium when it heads to space in a launch scheduled for 2013.

Many of the more obscure elements are toxic, but some make better poisons than others. Thallium was certainly known to one mass murderer: Saddam Hussein. Iraq's brutal Baath dictator liked to use thallium sulfate as his weapon of choice to kill dissidents and activists.

Thallium is a slow-acting poison, which allows for cruel mind games. Saddam's guards and secret service would sometimes grant prisoners a full release after they'd drunk the poison, knowing they would die a gradual and painful death in the days to come.

The 55th element is one of the key ingredients in the smallest-ever spacecraft engine. The European Space Agency's Davide Nicolini says that the LISA Pathfinder, set to launch at the end of 2009, will travel to the Lagrange Point 1, the spot where Earth and the sun's gravitational fields balance each other out.

To stay in that exact spot, the craft will use a field emission electric propulsion engine, which ejects ions of liquid metal cesium to exert a miniscule thrust to counter tiny forces on the craft, such as the sunlight itself.

In 1989, physicists Stanley Pons and Martin Fleischmann dropped a bombshell of an announcement, claiming to have achieved desktop cold fusion. The energy crisis was over; all you needed was palladium electrodes and heavy water to achieve the room-temperature fusion of deuterium, a heavier isotope of hydrogen. It would be a new and clean way to power the planet.

There was just this one problem: No other scientists could reproduce the two physicists' results, and cold fusion research took a huge P.R. hit. But while the cold fusion fiasco destroyed the scientists' careers, palladium lives on in simpler applications like electronics, dentistry, and holding up your pants: this is a Swiss-made palladium-plated belt buckle.

In World War I, cavalry warfare gave way to primitive tanks for the first time. The British had the first tanks, but their manganese-steel plates couldn't take the full shock of a shell. Fortunately for the Brits, their ally, France, had created molybdenum-steel armor plating that could provide better protection at one-third the thickness. This WWI tank sits in London's Imperial War Museum.

Molybdenum has an exotic connection as well: A Russian mission called Luna-24 turned up a minute particle of nearly pure molybdenum on the moon, the first time it had been located there.

Bismuth is a brittle metal with a pink hue, and it lends its name and color to a famous household item: Pepto-Bismol.

Humans have been using bismuth for centuries; researchers found bronze made with 18 percent bismuth in the ruins of Machu Picchu, Peru. The element has been a medical ingredient for more than a century--though, presumably, medicine didn't taste so much like bubble gum back then.

There's no Superman, and there's no such thing as kryptonite, either--at least not one that glows green and contains the element krypton. In the newest installment of the movie series, 2006's Superman Returns, super-villain Lex Luthor reveals the mineral's made-up chemical formula to be sodium lithium boron silicate hydroxide, but geologists unearthed something with that very structure in Serbia in 2007. However the real-life mineral isn't called kryptonite because krypton already exists--it's a noble gas and nowhere to be found in the newly found mineral, which the discoverers dubbed jadarite.

Krypton is useful, however, and is often employed in fluorescent lamps. Top-of-the-line double-insulated windows also use krypton gas rather than argon or plain old air for insulation. Just don't try to use it to neutralize superheroes.