Scale: 10^-13 meters = 100 fm = 100 femtometers

The Nucleus

The tiny nucleus of stable carbon contains 12 nucleons (protons and neutrons). How much larger would the nucleus be for a uranium atom, for example ²³⁸U? A simple calculation shows that even the largest nuclei would fit within a sphere with a diameter not much larger than the diagonal of one of the small center squares. Recall that the volume of a sphere is . If we let r be the radius of the carbon nucleus, then the white sphere in the picture has radius 3r. So the volume of the sphere is , or 27(), 27 times the volume of the carbon nucleus. Since there are 12 nucleons in the carbon nucleus, we could squeeze as many as 27 x 12 = 324 nucleons inside the white sphere – easily more than enough for ²³⁸U.