What is the most expensive element? This question is tricky to answer because some elements simply cannot be purchased in pure form. For example, the superheavy elements at the end of the periodic table are so unstable, even the researchers studying them typically don't have a sample for more than a fraction of a second. The cost of these elements is essentially the price tag of their synthesis, which runs into millions or billions of dollars per atom.

Here is a look at the most expensive natural element and the most expensive of any element known to exist.

Most Expensive Natural Element

The most expensive natural element is francium. Although francium occurs naturally, it decays so quickly that it cannot be collected for use. Only a few atoms of francium have been produced commercially, so if you wanted to produce 100 grams of francium, you could expect to pay a few billion U.S. dollars for it. Lutetium is the most expensive element that you could actually order and purchase. The price for 100 grams of lutetium is around $10,000. So, from a practical standpoint, lutetium is the most expensive element.

Expensive Synthetic Elements

The transuranium elements, in general, are extremely expensive. These elements typically are man-made, plus it is costly to isolate the trace amounts of transuranic elements that exist naturally. For example, based on the cost of the accelerator time, manpower, materials, etc., californium is estimated to cost around $2.7 billion per 100 grams. You can contrast that price with that cost of plutonium, which runs between $5,000 and $13,000 per 100 grams, depending on purity.

Fast Facts: The Most Expensive Natural Elements The most expensive natural element is francium, but it decays so quickly it can't be collected to be sold. If you could buy it, you'd pay billions of dollars for 100 grams.

The most expensive natural element that is stable enough to purchase is lutetium. If you order 100 grams of lutetium, it will cost about $10,000.

Atoms of synthetic elements cost millions of dollars to produce. Sometimes they don't even last long enough to be detected. Scientists only know they were there because of their decay products.

Antimatter Costs More Than Matter

Of course, you could argue that anti-elements, which technically are pure elements, are more expensive than regular elements. Gerald Smith estimated that positrons could be produced for about $25 billion per gram in 2006. NASA gave a figure of $62.5 trillion per gram of antihydrogen in 1999. While you can't buy antimatter, it does occur naturally. For example, it is produced by some lightning strikes. However, antimatter reacts with regular matter very quickly.

Other Expensive Elements

Gold is a valuable element, worth around $39.80 per gram. While it's much less costly than lutetium, it's also easier to obtain, more useful, and easier to trade.

Like gold, rhodium is an element that is a noble metal. Rhodium is used in jewelry and catalytic converters. It's worth around $45 per gram.

Platinum has value comparable to that of rhodium. It's used as a catalyst, in jewelry, and in certain drugs. It costs around $48 per gram.

Plutonium is a radioactive element that can be used for research and nuclear applications. It's worth about $4,000 per gram (although you can expect various regulatory agencies to take a close look at you if you start accumulating it).

Tritium is the radioactive isotope of the element hydrogen. Tritium is used in research and to illuminate phosphors as a light source. It costs around $30,000 per gram.

Carbon can be one of the least expensive elements (as carbon black or soot) or most expensive (as diamond). While diamonds vary widely in price, a flawless diamond would run you upwards of $65,000 per gram.

Californium is another radioactive element, used primarily in research and in instruments employed in the petroleum industry. A gram of californium-252 can cost $27 million per gram, which makes it considerably more expensive than lutetium, but less than francium. Fortunately, only a tiny quantity of californium is needed at a time.

Elements That Are Dirt Cheap

If you can't afford francium, lutetium, or even gold, plenty of elements are readily available in pure form. If you've ever burned a marshmallow or a piece of toast, the black ash was nearly pure carbon.

Other elements, with higher value, are readily available in pure form. The copper in electrical wiring is over 99 percent pure. Natural sulfur occurs around volcanoes.