Going to be a different atom once you walk near. Or temperature changes, the wind blows, and so on.
We’ll need to give each atom a unique ID. That would solve the problem.
No man steps into the same 14-digit-precision geocoördinate twice.
You're going to run into problems with quantum mechanics and the non zero amplitude that two identical hydrogens swap place.
Let's start with electrons. I've got SN001 here with me, but I haven't been able to find any others...
https://en.wikipedia.org/wiki/One-electron_universe