Question: What Is the Hardest Element?
Answer: The hardest pure element is carbon in the form of a diamond. Diamond is not the hardest substance known to man. Some ceramics are harder, but they consist of multiple elements.
Not all forms of carbon are hard. Carbon assumes several structures, called allotropes. The carbon allotrope known as graphite is quite soft. It is used in pencil 'leads'.
Different Types of Hardness
Hardness depends largely on the packing of atoms in a material and the strength of interatomic or intermolecular bonds. Because the behavior of a material is complex, there are different types of hardness. Diamond has an extremely high scratch hardness. Other forms of hardness are indentation hardness and rebound hardness.
Other Hard ElementsAlthough carbon is the hardest pure element, metals generally are hard. Another nonmetal -- boron -- also has a hard allotrope. Here is the Mohs hardness of some other pure elements:
Boron - 9.5
Chromium - 8.5
Tungsten - 7.5
Rhenium - 7.0
Osmium - 7.0
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