Chapter 2, Problem 90QAP

Calculate the average density of a single Al-27 atom by assuming that it is a sphere with a radius of 0.143 nm. The masses of a proton, electron, and neutron are $1.6726\times {10}^{-24}\text{g},9.1094\times {10}^{-28}\text{g}$, and $1.6749\times {10}^{-24}\text{g}$, respectively. The volume of a sphere is $4\pi r^3/3$, where r is its radius. Express the answer in grams per cubic centimeter. The density of aluminum is found experimentally to be

2.70 g/cm³. What does that suggest about the packing of aluminum atoms in the metal?