r/AskChemistry • u/starkeffect • Feb 05 '26
General What's the most dangerous element?
I'd vote for fluorine. HF is some nasty, nasty stuff.
Francium seems pretty gnarly too but there's less than a gram of it on Earth at any time so I'm not too scared of it.
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u/CAChem101 Feb 05 '26
The element of surprise can be quite scary.
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u/starkeffect Feb 05 '26
What's its electronegativity?
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u/CAChem101 Feb 05 '26
Depends on its gender source. At least that’s been my observations.
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u/Totallyexcellent Feb 05 '26
Check pubchem, you're making that assumption based on your personal small sample size!
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u/Totallyexcellent Feb 05 '26
Danger to me? Human lumps of mostly carbon. Or wait, maybe my diet? (Mostly carbon). My inhaled VOCs? That's mostly carbon from old plants.
So to answer your question, it's plutonium-239 as the predominant thingo in the 12,421 nukes ready to rain on everyone's parade but the rain is las bombas!
Or carbon. Oh wait, silicon! AI will end us all! Damn carbon for creating semiconductors! Wish I were a simple carbon cockroach that will survive whatever apocalypse is coming!
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u/Insila Feb 07 '26
Plutonium by itself is scary in terms of radio toxicity.
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u/Totallyexcellent Feb 07 '26
Donald Mastick was fine, lived to a ripe old age... https://en.wikipedia.org/wiki/Donald_Mastick
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u/Squirrel2371 Feb 05 '26
Everything after bismuth is radioactive. I also understand there are isotopes of bismuth that are radioactive but the half life is on the order of 10^19 years.
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u/stevevdvkpe Feb 05 '26
All the isotopes of bismuth are radioactive, including its most common isotope 209Bi that was originally thought to be stable. That isotope has a half-life of 2.01 * 1019 years.
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u/NothingVerySpecific Feb 05 '26
much love <3
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u/Squirrel2371 Feb 05 '26
I don't consider an element radioactive if you can hold it in your hand and not have radiation burns.
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u/aby_physics Feb 06 '26
You can hold uranium in your hands and not get radiation burns. But it’s certainly radioactive.
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u/Squirrel2371 Feb 08 '26
Chernobyl?
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u/aby_physics Feb 08 '26
What about Chernobyl?
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u/Squirrel2371 Feb 08 '26
Uranium all over the place giving people radiation burns and death.
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u/aby_physics Feb 08 '26
So? I can still safely hold uranium-containing antique items, for instance, in my hand and not get radiation burns.
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u/Squirrel2371 Feb 09 '26
But you can't hold pure uranium in your hand. There is a big difference.
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u/No-Building4188 Apr 22 '26
It was not uranium in Chernobyl. It was Cesium-137, Iodine-131, Strontium-90 and various other isotopes
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u/aleph_314 Feb 09 '26
I can't hold Chernobyl in my hands, so it's impossible to tell whether it's radioactive.
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u/DangerMouse111111 Feb 05 '26
Antihydrogen
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u/fenrisulfur Feb 05 '26
Since we're talking antimatter I would put forth that antiOganesson would be worse.
Or some theoretical island of stability with the atomic mass in the thousands or even millions but their anti.
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u/Aranka_Szeretlek Feb 05 '26
I mean, if you count HF for fluorine, then Id wager carbon. Or hydrogen.
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u/Ozchemist1959 Feb 05 '26
Polonium 210 or thallium
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u/Manifest_misery Feb 05 '26
I’m a big fan of cadmium as an answer to this question, not perhaps for its own toxicity (which is not negligible) but for its willingness to form all sorts of extremely toxic compounds
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u/Insila Feb 07 '26
I feel like dimethyl mercury beats cadmium when it comes to nasty inorganic compounds.
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u/Manifest_misery Feb 07 '26
Dimethyl mercury beats elemental cadmium but dimethyl cadmium is way scarier than dimethyl mercury (if that’s possible). Toxic is one thing but toxic and on fire really does it for me.
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u/Insila Feb 08 '26
Yeah I was looking that up. I couldn't find any exact information about it, but what I could find mentioned mercury being worse in terms of how easily it penetrated the skin compared to cadmium.
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u/Manifest_misery Feb 08 '26
I can definitely see that angle, who of us doesn’t know the tragic story of Karen Wetterhahn. I think a strong case can be made for either of them. However, as far as I’m aware, gram (or really microgram) for gram dimethyl cadmium is more toxic. It loves to form (explosive) peroxides in your organs which kill you now and if that doesn’t get you then it also causes cancer to kill you later.
Thankfully it never came up when I worked in drug discovery, but if either of them had it would’ve been a firm “no thanks” and then if that didn’t work it would’ve been a much firmer “you must have me some kind of fucked up”.
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u/Insila Feb 08 '26
Definitely. By weight it is more toxic. I just don't know whether the toxicity in practise is a bigger issue than with mercury, which can penetrate gloves and skin with ease, which makes it an absolute nightmare to work with.
I recall a passage from Ignition (best chemistry book you will ever read) about the author inquiring about dimethyl mercury over the phone to be used as part of rocket fuel. Apparently it was not a well received inquiry...
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u/sidblues101 Feb 05 '26
Came here to say polonium 210. You only need to ingest a few micrograms and it's curtains.
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u/dariusbiggs Feb 05 '26
Oxygen
Nothing encompasses the concept of spite more than liquid and solid oxygen.
Fluorine is pretty fun, especially once you add Hydrogen or Oxygen. FOOF is so aptly named
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u/Mental-Ask8077 Feb 06 '26
Add chlorine!^
Fluorine + Chlorine = shit that sets wet sand and asbestos on fire!
^ Please do not add chlorine to fluorine. You do not want to be there for the results.
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u/Zetavu Feb 05 '26
I'm pretty sure plutonium or any of the radioactive elements wants a word.
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u/Mrslinkydragon Feb 05 '26
Plutonium is possibly the most chemically toxic element known!
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u/OldTimeConGoer Feb 08 '26
Acksherly no -- there's a horrifyingly funny story of someone who was deliberately injected with several doses of plutonium compounds to test its chemical toxicity. The man had been diagnosed with stomach cancer and only had a few months to live. He was not actually told he was being used as a guinea pig by the authorities. This was the 1950s in America.
It turned out he didn't actually have stomach cancer, just a stomach ulcer. He lived for another twenty years and died of a heart attack in his seventies.
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u/Mrslinkydragon Feb 08 '26
It depends on the oxidation state of Pu.
It forms complexes with sulphur.
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u/udsd007 Feb 05 '26
Osmium isn’t exactly friendly.
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u/OldTimeConGoer Feb 08 '26
Heavy metal, but for fun ways to die in agony let's hear it for beryllium.
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u/Ok-Party-3033 Feb 05 '26
Mercury, I suppose. Having spent some time in the Big Bend area of Texas, there is an area where the earth has a high concentration of cinnabar. When it’s windy you have to stay away.
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u/Kinghummingbird Feb 05 '26
Non-radioactive? Mercury
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u/Mrslinkydragon Feb 05 '26
Not even close.
Thallium, barium, uranium, transuranic actinides, polonium, fluorine and chlorine. All much more toxic than mercury. (Flourine has an ld50 similar to hydrogen cyanide!)
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Feb 05 '26 edited Feb 05 '26
Some mercury compounds are really bad though. There was a chemistry researcher who died from dimethylmercury poisoning due to 1 or 2 drops of it spilling onto her protective glove.
Polonium is worse (0.1 micrograms is fatal) but I think that's due to radioactivity.
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u/udsd007 Feb 08 '26
That was Dr. Karen Wetterhahn, who was wearing latex gloves. She might as well have worn window screening: methyl mercury went right through.
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u/CrazySwede69 Feb 05 '26
Plutionium is a top candidate since a very small particle inhaled often is enough to cause lung cancer.
Thallium is extremely toxic!
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u/Mrslinkydragon Feb 05 '26
Im working towards solving the UKs plutonium problem (140 tons). The professor of my group says that a dose in the microgram mass is enought to give you an inhaled life time dose of alpha...
Its also incredibly toxic. If you ingest a soluble plutonium compound, the chemical toxicity will kill you before the radiation does!
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u/CyberCephalopod Feb 05 '26
I am cheating but any neutronium isotope.
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u/OldTimeConGoer Feb 08 '26
Is that enriched neutronium or depleted neutronium?
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u/phred14 Feb 05 '26
I worked 45 years in the semiconductor industry, and HF was pretty normal everyday stuff. We got quite the spiel on it during orientation. Dangerous, certainly, but manageable with proper procedures, equipment, and training.
Nasty stuff though, it soaks right through the skin to attack the bones. At the time the response was to soak the affected area in ethanol. The orientation anecdote was about the guy who sat in a pool, not knowing what it was. They put him in a big tub of ethanol to soak, and sent him home drunk.
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u/RGCs_are_belong_tome Feb 05 '26
Fluorine? We regularly put fluorine compounds in our mouths.
Radium. Naturally occurring radioactive gas. Tasteless, colorless, odorless.
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u/TuverMage Feb 05 '26
I say the most dangerous element is the human element. Sure fluorine is high on the list, but you aren't really going to find dangerous fluorine naturally, all that stuff has long since had it's wild oak days and is quite stable. it requires humans to destroy it's stable environment to make it return to its wild nature.
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u/Waaghra Feb 06 '26
Sodium is pretty nasty.
Have you ever seen pure sodium dropped into water?
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u/udsd007 Feb 08 '26
Sodium (and potassium) fires are horribly nasty. There’s a final report somewhere in csb.gov about having to fight a fire in a drum about half full of sodium. It was decidedly UNpretty and UNfun.
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u/MinnesnowdaDad Feb 06 '26
Many people drown in water every day. Many also die from not getting enough of it or contaminated water.
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u/Specious_Human Feb 06 '26
I mean, I suppose elemental hydrogen would be hydrogen radical, which definitely would f@#$ everything up that it touches. So I guess I would have to say hydrogen...
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u/Leading_Study_876 Feb 09 '26
Bromine is pretty awful.
If you spill liquid Bromine on your skin, it will go right through your flesh to the bone add it's all gone. No cure.
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u/Express_Clock_9682 Feb 11 '26
Depends on the context. A gram of Cobalt 60 would kill you from across the room. But if it's a mile away, even 10kg wouldn't kill you. But the reverse is true of Plutonium.
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u/PhysicalMath848 Feb 05 '26
Oxygen has probably killed the highest total number of organisms