The size of an atom is primarily determined by the distribution of its electrons, while the size of the atomic nucleus is determined by the number of protons and neutrons it contains. In a typical atom, the size of the nucleus is much smaller compared to the overall size of the atom.
If, hypothetically, an atom were to have an electron cloud larger than its nucleus, it would imply that the electron cloud extends significantly beyond the region occupied by the nucleus. This situation is not observed in stable atoms as the electrons are bound to the nucleus by the electrostatic attraction between the positively charged protons in the nucleus and the negatively charged electrons.
However, it is worth noting that there are certain atomic and subatomic systems, such as highly excited or ionized atoms, where the electron cloud can be significantly expanded or distorted due to specific conditions. These systems might exhibit electron distributions that are larger or more spread out compared to their nucleus. Nevertheless, these cases usually involve a temporary or highly specialized state and are not characteristic of stable, neutral atoms.
In summary, in a stable atom, the electron cloud is typically larger in size than the atomic nucleus, and the electron-nucleus interaction keeps the electrons bound to the nucleus. The electron cloud and nucleus have a specific balance in size and charge distribution that ensures the stability and integrity of the atom.