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loci_existentiae t1_jbyw309 wrote

Reply to comment by robot_egg in How do the physical properties of the isotope Iron-54 differ from the more common Iron-56? by Colonel__Kernel

Thank you for this cogent easy to understand answer for folks like myself.

Does Fe-54 conduct electricity in the same way as 56? Is it as magnetic? And do we find it commonly enough to build with it like we do with 56? (Last one I'm guessing is a big no and we may never know if we were using it in our materials.)

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robot_egg t1_jbyywyg wrote

I'm an organic chemist, not a metallurgist. I believe that conductivity and magnetism would be the same, but it's a little outside my wheelhouse.

You're not going to find pure Fe-54 or -56 in nature. They'll be mixed in more or less the natural abundance ratio anywhere you find iron. It's certainly possible to separate them; much easier than enriching uranium.

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mfb- t1_jbznvga wrote

As long as you don't go to nuclear physics, they behave essentially the same apart from the small weight difference. Conductivity, magnetism and so on is all determined by the behavior of the electrons which don't change here.

The isotope ratio of iron is essentially the same everywhere for the same reason: There is no natural process that would separate them or even accumulate one isotope much more than the other. No matter where you get your iron from you'll have 5.85% of Fe-54 and 91.75% of Fe-56 with only really tiny variations. Artificially you can separate them, if you absolutely want a sword that's 4% lighter.

For iron no one cares, but for uranium these isotope ratios are closely monitored to make sure no one steals it or tries to extract enriched uranium or similar. That's why it was a big deal when uranium from a mine in Oklo had just 0.6% uranium-235 (the main isotope used in reactors and nuclear weapons) instead of the normal 0.72%. Did someone steal something? Turns out this site had a natural fission chain reaction two billion years ago, reducing the amount of U-235.

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luckyluke193 t1_jbzknt1 wrote

It's extremely rare to have qualitative changes in physical properties due to a change in isotopes. Normally, phase transformations occur at slightly different temperatures, and that's about it.

The only example I can think of is SrTiO3, which becomes ferroelectric at cryogenic temperatures when common oxygen 16 is replaced by the rarer oxygen 18.

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