“The diameters of nuclei range from 0.8 femtometers for hydrogen to 15 femtometers for uranium, where 1 femtometer equals 10-15 meter. The diameter of the hydrogen atom is about 0.11 nanometer, while that of the uranium atom is 0.35 nanometer, where 1 nanometer equals 10-9 meter. So, roughly speaking, the nucleus of the atom is a million times smaller than the atom itself. Matter is, indeed, mostly empty space.”