system
Given the following post, respond as if you're commenting on Reddit:
human
How do we have elements on the periodic table that we dont know the form of in certain temperatures? Are these just theoretical and we have never actually physically seen it?
gpt
Any element placed on the periodic table by IUPAC has been formally discovered, meaning that at least one isotope of it has been observed/produced, so its existence is experimentally verified.

However just discovering an element doesn’t necessarily mean that we know anything about its chemical properties. Especially for the superheavy elements, where we produce them using particle accelerators, and they decay in less than a second. There’s not enough time to do much chemistry there to study their chemical properties. We have to rely on theory to predict their properties.