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I'm considering a world where there's an element that has an element that's naturally a plasma. I'm wondering what the broad behavior of such an element would be. Would it be inherently unstable, dissipating quickly?

How difficult would it be to change to another state - say someone is using this plasma to fuel magic and another person lowered the temperature to where it was useless because it became a gas or a liquid.

What kind of atomic properties might we expect such an element to have?

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    $\begingroup$ Extrapolating a bit: In essence, a plasma is just a substance with too high of an internal energy that the electrons gets stripped from the nucleii. So your "room-temperature plasma" would just be an highly reactive gas - I would guess, it would probably rather similiar to Ozone (O3) $\endgroup$ Commented Jun 5, 2022 at 21:19
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    $\begingroup$ If its electronegativity is that low, it might need to me mostly made of neutrons and thus very radioactive. $\endgroup$
    – John
    Commented Jun 5, 2022 at 23:22
  • $\begingroup$ If it's throwing away its electrons at room temperature, it will be highly chemically reactive and form ionic compounds with just about anything. The only way it could exist in a plasma state is if you isolate it by putting it in a (chemically inert) sealed container. In terms of properties, cesium is a good starting point. Plasma formation is related to first ionization energy, which isn't really correlated with boiling point, so you could set those two numbers independently if you like. $\endgroup$ Commented Jun 6, 2022 at 3:56
  • $\begingroup$ The plasma itself probably wouldn't dissipate all that much if kept in a vacuum as it will be bound together by its own electrostatic charge. But chemical reactivity is a given. But, magic, so, whatever... $\endgroup$ Commented Jun 6, 2022 at 3:58

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I'm considering a world where there's an element that's naturally a plasma. I'm wondering what the broad behavior of such an element would be. Would it be inherently unstable, dissipating quickly?

It would dissipate as quickly as any gas would. So, under most circumstances, yes, pretty quickly. If it's extremely heavy, though, it might hang out in depressions for a good long while, like, for example, sulfur hexafluoride gas does. That's actually not implausible--to be a plasma at room temperature, you'll want something that's gaseous at room temperature and has a very loose hold on its outermost electrons. Something like a superheavy noble gas might fit the bill. Say, element 150 (underneath Oganesson) or 182, if they were magically stable.

How difficult would it be to change to another state - say someone is using this plasma to fuel magic and another person lowered the temperature to where it was useless because it became a gas or a liquid.

As difficult as you want, since you're making up a magical substance. But, the boiling points of noble gasses steadily go up as you go down the table, with radon boiling/condensing at a mere -71.6C; compare to xenon at -108C or krypton at -153.4C. So if you go with the superheavy noble gas model, it wouldn't be too ridiculous to extrapolate a condensation point of, say, -20C or so. And it would probably stop being usefully ionized well above that temperature, at low temperatures that are not too terribly difficult to reach.

What kind of atomic properties might we expect such an element to have?

Whatever you want, because magic. As a plasma, though, the bulk element would be a very good conductor of electricity, and a very good disinfectant--all those free electrons whizzing around are bad news for microorganisms, and would be bad news for you if you inhaled it!

Sticking with the superheavy noble gas model, it would probably form fluorides, chlorides, and bromides, and maybe iodides. Or, with at least one electron stripped off in its room-temperature state, it might behave like a heavy halogen and form weirdly charged salts. Additionally, due to usually-being-charged (because ionized), I would expect it to be strongly soluble in water, as well as strongly soluble in ammonia (which it would tend to turn blue, due to solvated electrons).

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    $\begingroup$ Why would you expect a row 9 noble gas to hold it's electrons weakly? Noble gases have a good grip on their electrons. $\endgroup$ Commented Jun 6, 2022 at 0:26
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    $\begingroup$ @LorenPechtel Because of being in row 9. First ionization energies go down as you move down the rows. And empirically, heavier noble gasses do give up electrons more easily, such that xenon is able to form more covalent compounds than any lighter noble gas, and krypton can form more than argon. A row 9 or 10 alkali metal would probably ionize even more easily, but it also wouldn't be a gas. $\endgroup$ Commented Jun 6, 2022 at 0:35
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    $\begingroup$ Reactivity goes up as you go down the rows but I can't imagine even a row 9 noble that would give up electrons that easily and not just grab them again. Look at Christopher's answer for what I'm thinking. $\endgroup$ Commented Jun 6, 2022 at 1:29
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"Cold plasma" is a real thing. In short, the molecules are ionized, but only the electrons have a high temperature. The cold ions have most of the mass, so the net temperature is low. This is a very short-lived condition, as the electrons rapidly get cooled down and the plasma returns to a neutral gas.

Being "naturally a plasma", your substance may not act as you'd expect a plasma to. Much of the use of a cold plasma is due to the tendency of the charged particles to find a way to form normal matter, even if it involves normally-unlikely chemical reactions that result in reactive or unstable chemicals like ozone or radicals, or the byproducts of neutralization like UV radiation. All of these render it no longer a plasma, which you don't want.

Your substance must naturally avoid these things...so it must not have normal electrons, or nuclei that form neutral atoms with normal electrons. It would have things analogous to electrons and nuclei, but which do not form stable neutral atoms or take the places of their normal matter counterparts. Possibly it could have quite weird properties like being immiscible with air, giving it some protection from being diluted to the point of being unnoticeable. (And given this, you could have a whole parallel periodic table of such elements.)

Note: there are some similarities between metals and plasmas. Your substance could still be a plasma in liquid or solid form, in which case it would probably act much like a metal. With the above assumptions, it would be a quite inert metal/quasi-metal. Perhaps some higher melting point types would be treated as especially noble metals.

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Q: I'm considering a world where there's an element that has an element that's naturally a plasma. I'm wondering what the broad behavior of such an element would be. Would it be inherently unstable, dissipating quickly?

The last question: it will. Ionization will consume your material. Your element basically goes up in flames, when exposed to the atmosphere or affected by a little magic.

Glow

Fire / spontaneous combustion

A solution that does not require a new element. Plasma is the stuff fire is made of.. so you'll just need some heat. There is also spontaneous combustion. Why need a new element? There's Lithium.. Phosphorus..

Magnetron field

If you have a grape, a knife, and a microwave you don't mind potentially ruining, you can make plasma at home. (Warning: this may ruin your microwave.) The process is simple: you cut a single grape nearly in half, leaving a bit of skin connecting the two halves, then microwave it by itself.

https://www.vox.com/xpress/2014/12/3/7326643/grape-plasma-microwave

How does this work? In a microwave oven, there's a huge electromagnetic field, that makes most fluids to cook quickly. That is because in food, you have fluids conduct electricity, solubles like salts or acid make them even more conducting. A lemon is a very good conductor for electricity, so the magnetron's field will concentrate its energy on a piece of lemon skin and superheat it, eventually causing the material in the lemon to kick out its electrons and become plasma.

Now suppose in your world, for some reason, there exist very strong magnetic fields, locally.. or magic invokes certain fields.. your element (or particle) is a good conductor and present in the atmosphere, it would glow.

Spontaneous ionization: shake it

Some options exist, like Molecular autoionization and (more theoretical) Autoionization of atoms. For a visible plasma, you'll need some magic to transmutate your material into an autoionizing state. With your element, it may be easy to do that. Molecules can have vibrationally autoionizing "Rydberg states", in which the small amount of energy necessary to ionize a Rydberg state is provided by vibrational excitation.

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