Element Density and Hardness
Date: November 2007
Is there a direct correlation between density and softness
of metals, i.e, lead and gold are dense but soft, where as iron is less
dense but harder?
There is no "simple" correlation between the density and the softness
of metals I am aware of because the two properties depend upon various
properties of the metals. The density of a metallic element is dominated
by its atomic number and weight and how the atoms "pack" in the structure
of the solid.
The hardness of a metal is also related to the atomic number and weight
of the atoms, but is also much more sensitive to the bonding between
metal atoms. In general, the more complex the metallic structure, the
"harder" the metal will be. The two properties of metals, density an
hardness/softness, are not related in a simple way. To take an extreme
example: sodium and potassium are relatively light metals, but are very
"soft". You can cut them with a dull knife. Tungsten is comparatively
dense, but relatively very hard and brittle.
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Update: June 2012