HARDEST ELEMENT - 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. 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.

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Hardest Element

What Is the Hardest Element?

Mohs Scale and Elements

by Anne Marie Helmenstine, Ph.D. 

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

Anne Marie Helmenstine, Ph.D.

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor. 

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

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https://www.thoughtco.com/what-is-the-hardest-element-606624