The atomic number represents the number of protons in an atom's nucleus. Since protons are fundamental particles, there is no theoretical limit to the atomic number.
In theory, an atom can have an atomic number as high as we can imagine or calculate. However, as the atomic number increases, the stability of the nucleus becomes increasingly challenging due to various factors, such as the increasing electrostatic repulsion between protons.
Currently, the highest naturally occurring atomic number is 118, corresponding to the element oganesson (Og). Elements with atomic numbers higher than 118 have been created in laboratories through particle accelerator experiments, but they are highly unstable and quickly decay.
It's important to note that the discovery and synthesis of superheavy elements are active areas of research, and scientists are continuously exploring and attempting to create elements with higher atomic numbers in order to expand our understanding of the periodic table.