Density: atomic size and

Density. Atomic size, and therefore volume, is inversely related to density. Across a period, densities increase, then level off, and finally dip a bit at the end of a series (Figure 22.4D). Down a transition group, densities increase dramatically because atomic volumes change little from Period 5 to 6, but atomic masses increase significantly. As a result, the Period 6 series contains some of the densest elements tungsten, rhenium, osmium, iridium, platinum, and gold have densities about 20 times that of water and twice that of lead. 

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