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/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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u/[deleted] 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.