Solids and liquids have roughly comparable densities, while gases are far less dense than either. What accounts for the gap?

1. Density is mass divided by volume, so a low density means little mass spread through a large volume. 2. In solids and liquids the atoms are in close contact, which packs a lot of mass into a small volume. 3. In a gas the atoms are separated by large amounts of empty space, so the same number of atoms fills a far bigger volume. 4. The atoms of a gas are not intrinsically lighter, and they certainly carry mass, so those explanations fail. 5. A rigid lattice describes a solid, which is the dense case rather than the sparse one. _Source: OpenStax College Physics (CC BY 4.0), Ch 11 "Fluid Statics", section 11.2 Density_