Atoms are among the most fundamental building blocks of matter. Everything except energy is made of matter, which means that everything in the universe is made of atoms. Atoms are mostly empty space, however. The diameter of the nucleus of an atom -- the protons and neutrons in the center -- is 10,000 times smaller than the total diameter of the atom. This space contains electrons flying around the nucleus, but is mostly empty. Thus, we can compare the relative distances inside the atom and the comparative size of the atom.
Make the space in an atom easier to visualize by showing how small the nucleus is to the total size of the atom by comparing it to something familiar. According to Canada's National Laboratory for Particle Physics, if a golf ball represents the nucleus, the first group of electrons would be a kilometer away. The second group would be 4 kilometers away, and so on.
Compare the total size of an atom to the size of macroscopic objects. If we enlarged an atom to the size of a basketball, then the dime would become as big as our entire planet, according to the U.S. Department of Energy.
Enlarge a familiar object to illustrate the numbers of atoms packed into matter. For example, if an apple were enlarged to the size of the Earth, its individual atoms would be the size of regular apples. Another way to illustrate the sizes of an atom's parts is to imagine that the nucleus of an atom was the size of our sun. In that case, the closest electron would be beyond Mars.