The average person's idea of the size of an atom can vary greatly, as it is influenced by individual knowledge, education, and exposure to scientific concepts. However, many people tend to have a general understanding that atoms are extremely small particles that make up matter.
Historically, the concept of the atom being indivisible was first proposed by ancient Greek philosophers, such as Democritus. However, modern science has revealed that atoms are composed of even smaller particles, such as protons, neutrons, and electrons.
To provide a sense of scale, it is often said that atoms are on the order of angstroms (Å) in size. One angstrom is equal to 0.1 nanometers (nm) or 10^-10 meters. In terms of visualization, if we were to imagine scaling up an atom so that it was the size of a football stadium, the nucleus would be about the size of a marble in the center, while the electrons would be orbiting far away in the stands.
While this analogy can help in conceptualizing the relative sizes, it's important to remember that atoms are not solid objects like miniature balls. They are dynamic systems with a nucleus at the center, consisting of protons and neutrons, and electrons that exist in electron clouds or orbitals around the nucleus.
Overall, people's understanding of the size of an atom can vary, but it is generally accepted that atoms are incredibly small and require specialized tools and techniques, such as electron microscopes, to directly observe them.