I think the reason as to why Metalbenders can't bend Platinum is so they have a weakness. If they could bend all Metal; how would you stop them? Wooden weapons? Those break easily (especially against Metal). What could you make Tanks, Blimps, Mechs, etc. out of that wouldn't be bendable?
Metalbenders need a weakness. Otherwise; they might be near unstoppable. Imagine if Kuvira mech could have been bended. It wouldn't nearly have been the great threat it was. I think Metalbenders shouldn't be able to bend Platinum.
Weaknesses are great. The arc with Kuvira is great. Just because I believe bending of purer metals like platinum could be possible, doesn't mean I didn't want it to happen with the whole mech thing. That happened the way it should cause it had great storytelling and point. lol I just don't believe there really is a limit to the art of bending. Obviously it's clear not EVERYONE is going to reach that skill. Again, Toph still proved people wrong. Just because another bending element is found, doesn't mean a million people will have that skill. They also said many times in the series, that the so called boundaries are only an illusion (and with anything really). The thing is, if a platinum bender ever exist, or any other extra element, there's always going to be one above that one top that specific one, etc.
To everyone saying that this is a fair limitation, it really isn’t, though, because earth, bending has by far the least amount of abilities, when compared to every other bending outside of maybe fire bending but they have sozins commet don’t even get me started on water and then air benders can fly amongst a bunch of other things as well
@Lesbian4Kaido the atoms in pure metals and metal ore are connected. Delocalised electrons carry a charge, yes, but the atoms are still bonded together, even in platinum. So I don't think that's the reason behind it, especially because they could bend Mercury. It's likely there's a specific group of elements they're able to bend
@Actionmanrandell he C-C bonds, which is why they're very hard. They don't shatter because they can't absorb any energy, they shatter because once an atom in the the lattice is disrupted, the entire lattice collapses
You're making things more complicated then they need to be. In order to Metalbend; the Metal needs "Earth Impurities". You don't need to overthink it.
@Zealous Gamer then they wouldn't be able to bend Mercury or crystals, which they can
They never say it's Mercury. They say it's a Metal poison. It likely is Mercury but it isn't stated. It was also prepared which could mean Earth Impurities were added. Nothing about that was stated. It could also be that the Creators forgot their own rules when adding the poison. Or the poison already has Earth Impurities in it in the World of Avatar.
It was stated in the Show that Metal require Earth Impurities to be bendable. So, that is what I am going by.
As for Crystals; those were always bendable. They aren't the same as Metal.
@Zealous Gamer it was Mercury. Looks and behaves like Mercury. This wiki page also says it's Mercury. They can't have forgotten their own rules because they chained her up in platinum and said she can't bend her way out. What does "adding earth impurities" even mean? What do you think earth means?
Crystals are exactly the same as pure metals with regards to them being pure lattices. If they can't bend platinum because it's "pure" then they also can't bend pure crystals of any other non metallic elements. The only difference is where the elements sit on the periodic table, which means it does come down to chemistry.
Then you haven't been paying attention. They literally say in the show how Metal is bendable. As stated before; Crystals have always been bendable. We've see it long before Metalbending. The rules of bending are different from science.
What do you think?