Are there any useless elements?
January 10, 2011 8:47 AM   Subscribe

This question reminded me - I've been wondering what are the most useless naturally-occurring elements Are there any elements that have no known biological or commercial uses? And don't even make pretty shiny minerals?
posted by moonmilk to Science & Nature (14 answers total) 8 users marked this as a favorite
As a general rule, the higher the atomic number, the more technical, specific and arcane the uses of that element become. Carbon, hydrogen and oxygen are all of vital importance for a significant number of chemical reactions, whereas at the other extreme the lanthanides, actinides have very few uses indeed; those they do have are usually complicated. Even further, the so-called synthetic elements, such as ununpentium, ununquadium, etc, have no uses I know of.
posted by malusmoriendumest at 8:54 AM on January 10, 2011 [1 favorite]

Well the very highly radioactive elements are good candidates. Francium, for example, has a half-life of 8.5 hours despite being naturally occurring. As such, no one has found any uses for it, because it generally isn't around long enough to be used for anything.

Protactinium appears to have no known applications outside the laboratory. It's way more stable than francium, but it's an undesirable natural byproduct of uranium decay.

On the whole though, I think you'll find that almost every element has some kind of commercial industrial use, especially in creating alloys of more plentiful metals or in radioactive applications. Even astoundingly rare elements like astatine have medical technology applications.

There are, on the other hand, innumerable useless compounds. But even most of those aren't technically useless, as most of them can and occasionally do serve as rocks. It's just that it's usually cheaper to go out and get plain old gravel than to use industrial byproducts like slag.
posted by valkyryn at 9:01 AM on January 10, 2011 [1 favorite]

Don't think anything has zero uses, because even the rare ones at the bottom of the periodic table like thulium are used for various radiation-related users.

Given that, least useful would probably be radon.
posted by smackfu at 9:03 AM on January 10, 2011

malusmoriendumest , the lanthanides are rare earth metals and have many important, though specialised, uses.

The synthetic elements have half-lives too short to be useful for anything except research.
posted by James Scott-Brown at 9:03 AM on January 10, 2011

The synthetic elements have half-lives too short to be useful for anything except research.

But note that Technetium, though synthetic and radioactive, does have some important uses, particularly medical ones.
posted by jedicus at 9:17 AM on January 10, 2011

Response by poster: Thanks - this is great!

Radon once had "medical" uses!

Since anything at all can have "research applications," I'd say Francium is a good candidate for most useless element so far. Even Protactinium (which I was rooting for) can be used for radioactive dating of ocean segments.
posted by moonmilk at 9:25 AM on January 10, 2011

Response by poster: Segments? I meant sediments.
posted by moonmilk at 9:26 AM on January 10, 2011

As valkyryn says, essentially every element has a use of some sort if it can be obtained in quantity. There are some that have very limited use, like technetium, but even that artificial, exceedingly expensive element is an important medical diagnostic tool.

Probably the most "useless" elements are the radioactive transuranics, those elements with atomic number more than 92 (Uranium). The transuranides are all radioactive, all unstable (though some are very long-lived) and have very few uses outside of weapons and basic physics research. All are are artificial and are exceptionally expensive.

Even more "useless" than the transuranic are the subset of "superheavy" transactinic elements above atomic number 104. These are only fleetingly stable, with lives of thousanths of seconds or less. We have no idea of even basic the chemistry of most of the superheavies and could not make enough to do anything chemically interesting with them anyway. Still, even the most exotic of the superheavy transuranides have uses, and important roles, in testing our physical theories of matter. The "islands of stability" theorem is still a facinating possibility, for example.

So the least useful elements are the most expensive and the most unavailable, the transuranics to some degree and even more so the superheavys of Rutherfordium and heavier. My guess is that, if we could find to make these in quantity and at merely outrageous prices, then these would find use too. More and weirder electronic states are always useful to chemists and engineers. The rare earth lanthanides, which few thought had many uses, have revolutionized optics and electronics in the past twenty years, for example.
posted by bonehead at 9:36 AM on January 10, 2011

"Although currently there are no practical or commercial applications for any known berkelium isotopes, 249Bk has been used extensively as a target material for the production of still heavier actinides such as lawrencium. (source [pdf]).

Lawrencium itself has never been produced in macroscopic quantities.
posted by jedicus at 9:44 AM on January 10, 2011

Response by poster: I was a physics student at Berkeley long ago, so I'm happy to see Lawrencium and Berkelium show up here.
posted by moonmilk at 10:45 AM on January 10, 2011

Theodore Gray, the creator of the Periodic Table Table, relates the following story:
On an NPR program I was a guest on, the guest before me was John Emsley, author of "The 13th Element" which is all about Phosphorus, and a recent book that is a survey of all the elements. On the radio he said that the distinguishing characteristic of Thulium is that it is the most useless element. He could find no applications whatsoever to include in its section of his new book. That's pretty neat, I think.

Unfortunately, it isn't actually true: There are a number of industrial applications ranging from magnetostrictive alloys to lasers to x-ray sources for medical uses. Still, all in all, it is one of the more obscure of the elements.
posted by Johnny Assay at 10:57 AM on January 10, 2011

Let me recommend this totally awesome book, which includes a bunch of discussions like this.
posted by Sidhedevil at 11:40 AM on January 10, 2011

Holmium is used in electromagnets and in nuclear control rods (although other things work there as well). Not useless, but certainly not widely used.
posted by It's Never Lurgi at 2:34 PM on January 10, 2011

Response by poster: Thanks for all the great answers! Sidhedevil, I'm gonna check out that book.
posted by moonmilk at 7:54 AM on January 11, 2011

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