Question

How does atomic mass affect density?

Answer 1

there is no specific mathematical relation, but the elements who have biggest atomic mass (with the exception of the alkali metals and others who have also large volume) , have also high density (mass/volume).

Explanation:

Also in organic chemical if you insert an atom of a halogen element (especially bromine and iodine) the density of a hydrocarbon molecule increases very much.

Answer 2

There is no explicit relation that says the higher the atomic number, the greater the density. One should not assume that. One can assume that they are independent, however.

For example, gold (`"Au"`) has a density of `~~ 19.3 "g/cm"^3`, and its atomic number is `79`.

Silver (`Ag`) has an atomic number of only `47`, and its density is `10.49 "g/cm"^3`, so it does seem to follow this proposed trend.

However, osmium (`"Os"`) has an atomic number of `76`, yet its density is `~~22.57 "g/cm"^3`, which would clearly be an exception to this "trend". So, one can conclude that there is no foolproof trend that directly correlates density with atomic number.