What Is the Hardest Element?

Mohs Scale and Elements

Carbon is the hardest pure element, but only when it occurs in the form of a diamond.
Salexmccoy, Wikipedia Commons

Can you name the hardest element? It's an element that occurs naturally in pure form and has a hardness of 10 on the Mohs scale. Chances are you have seen it. 

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 Elements

Although 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

Learn More

Diamond Chemistry
How To Perform the Mohs Test
Most Dense Element
Most Abundant Element