What poison, specifically?
Several elements are poisonous all by themselves ... arsenic, chlorine, and fluorine to name a few. Lead isn't acutely "poisonous", but it (and several other elements) cause heavy metal toxicity. Plutonium will kill you via ionizing radiation. And so on.
Lots of elements are poisonous, and many others aren't poisonous themselves but do occur in poisonous substances. For example: fluorine, chlorine, and arsenic are all immediately toxic as elements, but hydrogen cyanide which is also pretty poisonous contains just carbon, nitrogen and hydrogen.
Arsenic.
carbon is used in rat poison and is the title of a murder mystery
it used to be lead, but most are steel now for environmental reasons. lead is a poison: a toxic heavy metal.
Arsenic
Arsenic. As. # 33
I think it can be used as making potassium cyanide (KCN) which is a harmfull and dangerous poison. It can be used to form CO i.e. carbonmonooxide which is also a toxic gas
Barium is used for rat poison.
iodine
Arsenic
arsenic
Most poison ivy lotions contain calamine, which is made of mostly zinc. The element Zirconium may also be used in some types of poison ivy lotions.
Barium is used as a rat poison.
arsenic
- alloying element for bronze - poison used by murderers
chlorine
arsenic
Several. Arsenic was once used as a rat poison and also has use in medicine (bone marrow disorders as an example. Thallium was once used as a rat poison and was once used to treat Syphillis Barium used to be used in rat poison and is used in medicine (barium meal) for some types of scan. Mostly these days however it is a compound that applies to both rather than an element - that being Warfarin.
bromide