Are there only a set number of atoms in the whole universe? As per the title, are there only a set number of atoms in the universe? Or does the universe make more atoms, and if so, how does it work?

I'm a high school student that just had a question during science class, I didn't ask my teacher, since he has more knowledge in biology than anything.
There are several processes at work:


Fission (of unstable elements) increases the number of atoms.
Fusion (occurs in stars and supernovae) decreases the number of atoms.
you could claim the formation of neutron stars decreases the number of atoms: it reduces atoms to just neutrons
you could claim the formation of black holes decreases the number of atoms: it moves atoms out of reach of the 'normal' universe. 


The next question is which of these processes produce/annihilate the largest number of atoms. Haven't found data for that yet. As Peter Erwin pointed out, any atom undergoing fission must have been built up from hydrogen and helium to start with.