Question: what are the most dangerous elements on the periodic table?
Answer: Polonium is One Nasty Element. Polonium isn't much worse than any other radioactive element, until it gets inside your body!. ... 
Mercury is Deadly and Omnipresent. ... 
Arsenic is a Classic Poison. ... 
Francium is Dangerously Reactive. ... 
Lead is the Poison We Live With. ... 
Plutonium is a Radioactive Heavy Metal.