These are all real elements. They decay within tiny fractions of a second to other stuff, so they're hard to make and study. Think of the nuclei as big, quiver

These are all real elements. They decay within tiny fractions of a second to other stuff, so they're hard to make and study. Think of the nuclei as big, quivering blobs of jelly. They are too big to hold together and really want to split into other stuff. But studying them while they're still in one piece tests our understanding of a lot of basic physics, and lets us compare predictions to reality.