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Posted Sep 4, 2001 by Orcus
Great article but Element 98 in the table is down as Gf not Cf.
Also, how can Promethium have only one naturally ocurring isotope when it is a synthetic element (ie. it doesn't occur naturally)?
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Posted Sep 5, 2001 by U255
Gf is now Cf! Thank you.  As for your other point, well, it's pretty hard chemistry and no one here can check it out thoughoughly and quickly. So, maybe, if you have time, see what the webelements site says about it all and get back to us.
All the best,
Sam.
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Posted Sep 5, 2001 by Orcus
I agree it's not exactly well known stuff but I can assure you that both Promethium (Pm) and Technetium (Tc) are the only two elements below Bismuth in the table that are radioactive and do not occur naturally on earth. I'm a professional chemist so hopefully I should know this stuff but The web elements site confirms this (quote 'there is no known promethium in the earth's crust).. It's only a small point though so I wouldn't worry too much
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Posted Sep 5, 2001 by beeline
Hi Orcus,
Sam was tempted to have a go because he's pretty proud of his O-level chemistry! 
I've looked at at the WebElements site, and the Promethium page seems to say (under the 'Isolation' heading) that Promethium in its metallic form is not found on Earth (as you say), but that compounds or promethium are - even though they're 'vanishingly rare'. After all, if it were not found anywhere here, then surely it wouldn't be available commercially (as it says it is) - creating it all artificially would be astonishingly expensive in a nuclear accelerator, wouldn't it?
You can probably assume that I've got the wrong end of the stick, so feel free to correct me!
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Posted Sep 5, 2001 by Orcus
Actually most radioactive elements you buy commercially are made in nuclear reactors Generating them there is indeed hellishly expensive - but not as expensive as extracting 1 femtogram from 4 million tonnes of ore
I would challenge you to find any element other than gold that *is* naturally found in its metallic form in the earth's crust - virtually all elements are far too reactive in their elemental form for that sort of thing.
My, this is a lot of chat for one silly point - really don't worry about it Only someone who's a trained chemist will spot it, and only if they read it very carefully.
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Posted Sep 5, 2001 by beeline
Ah - I see what you mean now - that its isotopes can't be 'naturally occurring' because it's synthetic. Sorry - I misunderstood you.
Although, according to that last link on the Entry page, "Promethium was found in minerals in 1926 by Harris and Hopkins in the US and independantly by Rolla and Fernando in Italy. Synthetic promethium was produced by H. B. Law in 1941. Promethium is very rare."
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Posted Sep 5, 2001 by Orcus
Actually I just got back from looking at Encarta - it seems it has been detected spectroscopically in various minerals. Interesting seeing as it's name 'promethium' is such because it was named after Prometheus - ie. synthetic.
OK - leave as is
What an interesting techy conversation we've had today
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Posted Sep 5, 2001 by Orcus
Oh yeah - Promethium 145 (it's most stable isotope) has a half life of 2.6 years. This is far too short for it to exist other than as a fission product from a heavy radioactive element such as uranium. So I guess it must be found alongside uranium or radium.
Ho Hum
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Posted Sep 6, 2001 by beeline
Yeah - that's what I thought - you just have to catch it 'at the right time' or it turns into something else. One of the less radioactive Lanthanides, I'd say, probably by alpha decay.
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Posted Sep 6, 2001 by Orcus
Well its a beta emitter I'm agraid and is the only radioactive lanthanide. It's the actinides that are radioactive
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Posted Sep 6, 2001 by Orcus
At least I hope they're not - I regularly use Ytterbium and noone's ever warned me if it is 
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Posted Sep 6, 2001 by beeline
Oh yes - I knew that.
What on Earth is Ytterbium used for? It doesn't seem to have any commercial uses... I note it was originally called Aldebaranium, presumably for the same reasons as the star Aldeberan...
Whoa - we're really geeking out here!
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Posted Sep 8, 2001 by Orcus
Ummm, it's er.... really techy chemistry.
I use Ytterbium triflate (Yb(OSO2CF3)3)) as a Lewis acid catalyst in reactions to open up an epoxide ring with various alcohols and amines.
But I expect you'd guessed that
You did ask
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Posted Sep 10, 2001 by beeline
Yeah, but I mean other than the obvious use...
I think we've reached the edge of my knowledge of physical chemistry! I did an 'A' Level back in the late 80s, but most of that stuff has 'gone to the tulips' since then. Don't get to practise it much now...
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