The nucleus of an atom can be modeled as several protons and neutrons closely packed together. Each particle has a mass of $1.67 \times 10^{-27} \mathrm{~kg}$ and radius on the order of $10^{-15} \mathrm{~m}$
(a) Use this model and the data provided to estimate the density of the nucleus of an atom.
(b) Compare your result with the density of a material such as iron. What do your result and comparison suggest concerning the structure of matter?