system
Given the following post, respond as if you're commenting on Reddit:
human
New chemical elements in space?

Is it possible that there are different chemical elements in space than those that are common on Earth?
gpt
New chemical elements - no.  Antimatter elements - sure.  Uncommon elements - sure.  

There are a lot of elements that aren't very common on earth that are more common in space, such as iridium (in asteroids), helium, etc.  There also may be anti-elements in space because there is no matter around to annihilate them.  But in terms of new elements in the periodic table, no.  That table is based on the number of protons atoms have.  You can't just fit new elements in between because you can't have atoms with a half-proton.  Elements with a different number of electrons are called ions and elements with a different number of neutrons called isotopes.  

On the subject of anti-elements though, we may one day find stable matter which is not comprised of atoms at all, quarks and gluons in strange and unpredictably stable arrangements which we haven't seen before.  But we haven't found anything like this yet, and there's nothing to suggest that it's even likely.