There are a few things that could be considered "fictional elements":
* Elements made up in fiction: Authors create elements for fantasy or science fiction stories. These elements have made-up properties and names, like "unobtainium" in the movie Avatar.
* Elements that haven't been discovered yet: Scientists are always looking for new elements, but some hypothetical elements have been predicted based on theories. These aren't "fictional" in the same way as the first category, but they are not currently known to exist.
Could you please clarify your question? Do you want to know about:
* Fictional elements from specific stories? If so, tell me the story and we can discuss the element.
* The process of creating elements in fiction?
* Hypothetical elements that scientists are searching for?
Once I know what you're interested in, I can give you a more precise answer!