The elements point is an interesting one. I'm trying to imagine what element or group of elements would be hard to do without. The elements related to carbon-based life of course (although hydrogen at least is not realistically scarce)--though I guess life doesn't need to be carbon-based. There are the conductive metals--gold, silver, copper--although aluminum at least could fill in in a pinch. Silicon? Although you'd probably have be lacking semiconductors more broadly.

If you restrict the discussion to worlds that are basically human habitable, also any trace elements that humans need. (According to this [1], humans are known to need 25 elements to live so that would be a good place to start.)

[1] https://www.sciencelearn.org.nz/resources/1728-the-essential...

Well something like platinum could be an important element (catalyses a lot of necessary processes). Its abundance will vary by a large amount across start systems. The earth is relatively rich in the element, so it is likely that we would have a comparative advantage here, but there could also be places like asteroids that have much greater amounts of this metal than us but smaller supplies of essential elements like phosphorous.

Stuff on the far right of the periodic table seems like prime candidates also, just because they're easy to lose and probably some of the hardest to obtain. Helium is basically a limited resource unless we figure out how to get it back out of the upper atmosphere; same goes for the argon we use for fire suppression - that stuff is already super expensive.

I'd assume if you can do interstellar travel, you can fuse hydrogen into helium. The other 8A elements? They're useful for various things but, in part because they are non-reactive, I'm not sure how essential they are for anything.

Argon and Helium are pretty stable though. It's probably cheaper to recover them from our atmosphere than to ship them from another planet altogether.

Our solar system is supposedly rich with phosphorus, but maybe any solar system with life would also be so blessed..

https://www.nature.com/articles/s41467-020-17649-9

Another one might be uranium.

Uranium is mostly just for fission though. Assuming the availability of fusion, probably a reasonable assumption given interstellar travel, I'm not sure you really need uranium very much.

You can use it to make plutonium for bomb pits. So far the only viable fusion devices are H-bombs triggered by such pits.

https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...

> That's a lot of material to mine, and it might be easier to import it.

That’s an energetically impossible claim.