After rutherford bombarded gold foil with alpha particles, he concluded that the volume of an atom is mostly empty space. which observation led rutherford to this conclusion

An atom is a particle of matter that uniquely defines achemical element. An atom consists of a central nucleus that is usually surrounded by one or more electrons. Each electron is negatively charged. The nucleus is positively charged, and contains one or more relatively heavy particles known as protons and neutrons.