What are the most extreme chemicals?
Densest gas
Densest element
Greatest range between melting and boiling temperature
Highest melting point
Lowest solubility product constant
Most dangerous: Is there any substance that&#39;s a 4-4-4 on the NFPA diamond?. But also, don't forget that the NPFA diamond doesn't even classify ClF3 as flammable (though everything else is flammable in it) and by any criterion it is far more dangerous than the other compounds in those answers)
Strongest acid
Strongest organic acid
Strongest reducing agent


Good external lists:


Most extreme compounds known to man.