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Name: George
Status: student
Grade: other
Location: TX
Date: November 2007


Question:
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?



Replies:
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.

Vince Calder



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