In addition to what other posters have said, I think some of it is just historical. Before we had the ability to manufacture & detect new isotopes & new elemen

In addition to what other posters have said, I think some of it is just historical. Before we had the ability to manufacture & detect new isotopes & new elements, we really did discover them. We could go poke around, explore new conditions that we hadn't explored before, and sometimes you'd actually discover a new isotope or element. Imagine you light something on fire, you capture the gasses and analyze them, and for the first time in human history you see sulphur. Did you manufacture the sulphur? Or discover it? Intuitively it probably feels like the sulphur was discovered but the uranium in the OP was manufactured, but really it's just a spectrum of how much work one needs to do to create the conditions that the universe requires to show you the element or isotope. Another interesting language question (IMO) is, once you can predict the existence of elements, their behavior, etc., what do you call it when you see the physical version for the first time? Did the person who first predicted the configuration & properties discover it? Did the person who created the physical version for the first time discover it? Did anyone discover it? Does it matter how much insight was required to make the prediction? Now that we're pretty good at predicting elements & isotopes, maybe the better way to phrase it is "discovered a process that produces xyz". Or if something unexpected happens, "discovered xyz is able to physically exist".