>How much would it weight A pound of it would weigh a pound. ;0) Do you mean how dense would it be? I don't know how well models predict density. But density

>How much would it weight A pound of it would weigh a pound. ;0) Do you mean how dense would it be? I don't know how well models predict density. But density is not proportional to atomic number or mass. Osmium has an atomic number of 76 and a density of ~23 g/cm^3. Uranium has an atomic number of 92 and a density of ~19 g/cm^3.