Why Atium had to be an alloy?

[lukaash]

This is a semicrackpot theory that I just came up with, but I was thinking about why Atium had to be an alloy. Of course now we know that pure atium has to be burnable by everyone because it is a god metal. But mabye there is another reason. 

What if Atium's pure form (without being combined with electrum) is light, gas, or plasma? I always found it really odd that Atium was a metal. It seemed very stable for Ruin's god metal. It would make a lot more sense if it was something destructive. We see the possibility for that with Etmetal (which I think it is related to Sazed in some way). It explodes on contact to water. It would be really interesting if Ruin's natural investiture was plasma or a more destructive element (a toxic gas?). Similar to how Honor's natural occurring investiture is light, it could be possible for other states of matter for metals. Shards have to specifically create solid god metal, and so preservation's work around was to just combined the natural formation of Ruin's investiture with an metal that has a wanted effect. Ruin couldn't combined it with a useless metal (aluminum) for example because that would not push people to burn it. Preservation wanted people to burn Ruin's god metal, so it combined it with a metal that it knew would create a powerful combination (alomancy is preservation's invested art after all).

[CryoZenith]

All types of investiture have a physical manifestation. All physical manifestations of investiture have a solid form. While yes, most Atium is actually an electrum-Atium alloy, it's still mostly Atium with impurities rather than an even-ish blend. Scadrian Atium is an alloy in the same sense that 99.97% purity gold is an alloy. You're *technically* correct that it's an alloy, but it doesn't have significantly different appearance or properties from the pure thing.