What is an approximate size for an atom?

An atom is typically around 0.1 to 0.5 nanometers in diameter, which is equivalent to about 1 to 5 angstroms. This size can vary based on the type of atom and its electron cloud. The nucleus, which contains protons and neutrons, is much smaller, on the order of femtometers (10^-15 meters). Overall, the vast majority of an atom's size comes from the space occupied by its electrons.