Chlorine gas was used as a poisonous gas in World War 1. It was one of the first chemical weapons employed in warfare and caused significant casualties and suffering among soldiers on the battlefield.
Arsenic is a commonly used element in rat poison due to its toxicity to rats and other rodents. It interferes with their ability to produce energy at a cellular level, leading to their death.
Chlorine is a greenish-yellow poisonous gas commonly used for disinfection and bleaching.
iodine is element 53
Arsenic.
bromide
A medicine that is poisonous, but was once used for medical treatment is Warfarin or Coumadin. These are both medicines used to thin the blood, but are also used in rat poison. Ether is also poisonous and was used in surgery to put a patient to sleep.
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.
an element that i think is a very old poison is mercury Antimony Arsenic Bismuth Mercury Copper Cadmium and Lead are all poisonous and used in old paint
Magnesium is used for fireworks and medicines
The seeds of the apple are poisonus. The poison is cyanide. This is the same poison Hitler used to go suicide.
Mercury is an element and is very poisonous. It is not used as a drug.
Lithium
Chlorine, which was used as a poisonous gas in World War I.
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.
iodine
Arsenic