As a subject matter expert in chemistry, I can tell you that determining the "rarest element in the world" can be a bit complex because rarity can be measured in different ways, such as abundance in the Earth's crust, difficulty of production, or even the stability of the element.

One element that is often cited as being extremely rare is astatine (At). Astatine is a halogen and the least stable of the naturally occurring elements. It has no stable isotopes, and its most stable isotope, astatine-210, has a half-life of only 8.1 hours. This makes it difficult to accumulate and study, contributing to its rarity.

However, there are other elements that are also considered rare, such as some of the superheavy elements that are created in laboratories and have no stable isotopes, like oganesson (Og), which is the last element in the current periodic table.

It's important to note that the concept of "rarest" can change with new discoveries and advancements in technology.

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Meet The Rarest Natural Element on Earth. It's so rare, there's just 30 grams TOTAL in Earth's crust. Named after the Greek word for unstable (astatos), Astatine is a naturally occurring semi-metal that results from the decay of uranium and thorium.read more >>