No Iron for your fair-folk maiden? (Part 1: alkaline)

Question

Excuse the broad question but I couldn’t resist making a metal pun.

So in my universe the Fair Folk encompass a large group of creatures. They live in their own little pocket universe, in which there is very little raw metal. Though they are all quite different, all of them share a few similarities.

1. They have a roughly humanoid body plan (emphasis on roughly)
2. They are not, nor have they ever been, human
3. They are all capable of manipulating ambient energy/internal energy, explaining their magic.
4. They are all weak to metals (not the music genre)

Some are weaker to certain types of metals than others, while some are immune to a specific metal, like a leprechaun with its gold. Each metal also causes a different effect on the fair folk which can be broadly broken down into 5 categories.

1. Alkaline/alkaloids: React very strongly with Fair Folk tissue.
2. Radioactive metals: Supercharge Fair Folk abilities, but rapidly kill them.
3. Iron type metals: Cause direct harm (iron causes burning and disrupts powers).
4. Silver type metals: Are toxic or drain energy from Fair Folk (silver is toxic)
5. Lead type metals: These cause odd effects (lead causes physical weakness, tin blinds them)

Iron type metals are near its group on the periodic table, the same is true for the silver and lead types. Some metals can be two different types at once, and alloys have all the effects of their component metals, but to a lesser extent.

So with all the exposition out of the way here is the question: What could cause the alkaline and alkaloid metals to react so extremely to fair folk tissue?

P.S. I realize there is a lot of information here for this question, but I plan on linking back to it in the future, so I figured I might as well do my explaining now, rather than having to go over all this again later.

Answer 1

One source of the strong reaction with alkali and alkali-earth metals could be a high level of weakly bound oxidizers in the Fair Folk flesh. Oxygen is common in our environment, and presumably in theirs as well, if they can breathe our air; chlorine is also fairly common, though not as an atmospheric gas. If their bodies contain any level of fluorine above trace levels, they'd be toxic to humans by touch, so I'll assume that's not the case -- but chlorine, loosely bound (in the form of chloride - ions) would react very vigorously with alkali and alkali earth metals, and also with aluminum and its close relatives.

Get the reaction started, of course, and the water in their bodies will get into the act -- which is what would start things for humans contacting, say, sodium or potassium metal. The presence of high chloride levels would simply make the reaction a bit more initially aggresive.

Answer 2

Alkaline and alkalis are really reactive metals.

(I assume you mean alkali when you say 'alkaloid', because alkaloids are an organic molecule classification. Alkaloids include morphine.)

I mean, there's really no point in overthinking this. Alkaline & alkaloids, due to their valence shell structures are pretty much dying to react with just about anything to get perfect valence shell structures and become like noble gases. Seriously, drop a stick of pure sodium in water and the stuff explodes. Sodium will even react with helium.

Humans react really strongly to alkali metals. A bar of pure sodium will explode violently in your mouth, form some really nasty compounds and give you burns. If you somehow swallow it, will proceed to melt through your stomach when reacting with stomach acid. Don't do it. And you notice how I keep mentioning sodium? It's the second-least reactive of the alkalis. The real nasty stuff is casesium and francium. (Yes, alkalines are dangerous too - includes stuff like magnesium, radium, and calcium.)

Also, last point.

They are all weak to metals (not the music genre)

This seems like a missed opportunity. I'm not saying you should do it, but this seems like a great foundation for a humorous short story.

Answer 3

You're asking why alkali metals (i.e. Group 1 on the periodic table: lithium, sodium, potassium, etc.) react strongly to fair folk tissue?

Easy. These metals react very strongly with water. And fair folk, being living creatures, are somewhere around 70% water. Go search YouTube for videos of people dropping alkali metals into water; there's plenty of them.

On contact with water, an alkali metal atom will transfer an electron to a nearby water molecule, creating a metal ion (which is inert), an OH¯ ion (which dissolves into the water, making it alkaline- hence the name "alkali metal"), and a free hydrogen atom. This hydrogen will link together with another hydrogen produced the same way, and leave the solution as hydrogen gas.

Oh, and this reaction also produces a lot of heat. So much so that it can quickly ignite the hydrogen it produces, which will combust with oxygen from the air, producing water vapor and even more heat.

Also, the alkali metals have quite low melting points, meaning that the heat produced by the dissolving metal and the burning hydrogen will soon cause what remains of the metal to melt. The hydrogen bubbles will cause the two liquids to mix in a chaotic and turbulent manner, greatly increasing the surface area of the metal- and therefore the reaction rate. Which, in turn, means more heat, more hydrogen, more turbulence, and more surface area, in an exponentially-increasing loop of positive feedback.

That's called a runaway chemical reaction.

That's also called an explosion.

So, yeah. If you want alkali metals to react violently to fair folk flesh, all you need to do is give your fair folk actual flesh. Don't make them robots or inorganic golems and you'll be fine.

If you also want to include the alkaline-earth metals in that (i.e. Group 2 in the periodic table; beryllium, magnesium, calcium, and the like), you'll need to do a little more work. Although these metals are still quite reactive as metals go, they're not as reactive as the alkali metals. Calcium, strontium, and barium will spontaneously react with water in a manner similar to the alkali metals, though I don't know how explosive this reaction is. Beryllium and magnesium, however, don't do this: instead, they form an insoluble oxide layer on their surface, protecting the metal underneath. If you want fair folk tissue to react violently with these metals, maybe you could have them secrete a strong oxidizer capable of igniting them on contact. ClF3 or FOOF should do it, though these seem like overkill to me, considering that they'll also burn concrete, water, and almost anything else. There's probably something tamer that'll still ignite beryllium and magnesium, perhaps by dissolving the oxide layer I mentioned and exposing the metal underneath.