- Density in solid state changes on change in atomic number of elements.

- Moving left to right in the period densities of solid and liquid elements first increases, it is maximum in the middle and then decreases.

- Moving upwards to downwards in a group, density generally increases but there is irregularity in this order.

- Density decreases instead of increasing on moving towards `K` in `IA` group and moving from `Mg` to `Ca` in `IIA` group. Because penultimate value of `K` and `Ca` increases, due to which density gets reduced.

- `Os` (`22.6` `gm//c c`) is most dense in solid elements and in liquids `Hg` is most dense (`13.6` `gm//c c`).