Everyone knows what Diamond is. But did you know that diamond is the hardest material found till date? It is so hard that nothing other than diamond can cut diamond. In this article, you will learn more interesting things about diamond, its properties, and its uses other than jewellery.
Structure of Diamond
Diamond is formed naturally under extremely high temperature and pressure conditions found only in the interior of Earth. Diamonds can be found about 90 to 125 miles below the Earth's surface. Depending on the conditions, a diamond stone may form within days or weeks, or it can even take millions of years.
Diamond is an allotrope of Carbon. That means it is one of the many forms in which Carbon forms molecules. The empirical formula of Diamond is just C - Diamond is made only of Carbon atoms!
Allotropes are different structural forms the same element can exist in.
Did you know that Diamond, Graphite and charcoal are all made up of just Carbon atoms? They are all allotropes of Carbon, and the empirical formula for all three is just C. The only difference between the three is the molecular structure i.e., the arrangement of atoms in space with respect to each other. Diamond has a structure called a tetrahedral. You will learn more about this in this article. If you're interested in Graphite, head over to Graphite.
The electronic configuration of Carbon is 1s2 2s2 2p2. It has 4 electrons in its valence shell and it needs 4 more to complete its Octet. So, it makes covalent bonds with 4 other Carbon atoms to do so.
The Octet rule of chemical bonding states that elements try to make bonds with each other such that they all have 8 electrons in their valence shell. Having 8 electrons in the valence shell is considered to be a stable electronic configuration.
A Covalent Bond is a chemical bond in which elements share electron-pairs with each other.
Carbon is a special element in the periodic table because of its ability to make stable long chains of bonds with other Carbon atoms (and sometimes occasional presence of other atoms). Diamond is formed when several (millions of millions) of Carbon atoms form long chains of bonds with each other, and arrange themselves in a tetrahedral structure.
A tetrahedral is a geometrical molecular shape. To visualize it, imagine a triangular pyramid (a pyramid with a triangular base). There is an atom at each vertex of the pyramid (there are 4 vertices in a triangular pyramid), and one atom is in the centre of the pyramid which is connected to all 4 atoms. This image will help you visualize it.
Fig. 1: 3D Tetrahedral Geometry | Wikimedia
In Diamond, each Carbon atom has 4 covalent bonds with 4 other Carbon atoms. A Giant Covalent Structure is formed when tetrahedrons after tetrahedrons of Carbon atoms are connected like a web.
Fig. 2: Tetrahedral Arrangement of Carbon Atoms in Diamond | Tutormyself
Properties of Diamond
The structure of Diamond and its chemical composition are responsible for the unique properties it has.
High Melting Point
To melt a material, the chemical bonds binding the atoms together have to be broken. Due to the presence of strong covalent bonds in the entire structure of Diamond, it takes a significant amount of energy to break them. The melting point of Diamond is about a blistering 4027oC!
High Hardness
Thanks to the presence of strong covalent bonds and a rigid tetrahedral structure, Diamond is the hardest material ever discovered.
Have you ever though how hardness of any material is measured? Hardness of mineral is measured by the Mohs Scale of Mineral Hardness. It is a scale which categorises hardness of materials in their natural form on a scale of 1 to 10, with 1 being the softest and 10 being the hardest. Diamond is a 10 the Mohs Scale of Mineral Hardness. Moreover, it is 40 times harder than the minerals on hardness level 9!
Are you thinking "If Diamond is the hardest material in the world, how is it cut into precise shapes for jewellery?"? Diamond is cut using high powered lasers. Laser cutting is an effective technology in general but is particularly useful for cutting Diamonds since nothing else can cut (or even scratch) them!
Low Coefficient of Friction
Friction on a material is caused by microscopic irregularities on the surface of that material. The structure of Diamond is a tightly packed solid structure which does not break easily even on the molecular level. Therefore, it has very less surface irregularities even on the microscopic level, giving it a low coefficient of friction.
High Thermal Conductivity
Diamond can conduct heat very efficiently - even more than some metals like Copper. This is due to the presence of stiff bonds and light Carbon atoms tightly packed together.
High Electrical Resistivity
There are no free electrons in the structure of Diamond (unlike Graphite, another allotrope of Carbon). Since there are no free electrons present, there is nothing to carry charge around in the structure. This results in high electrical resistivity.
Low Thermal Expansion Coefficient
Thermal Expansion Coefficient is a factor which tells how much heat is required to expand a material. Diamond does not expand with heat easily due to strong covalent bonds between Carbon atoms, and thus has low Thermal Expansion Coefficient.
Low Chemical Reactivity
The Carbon atoms in the structure of Diamond are very stable having completed their octet, and arranged in a stable structure. Therefore, they do not react with any substance even at higher temperatures. Due to low chemical reactivity, Diamonds are highly corrosion resistant.
Since Diamonds do not react with anything easily, they are biologically compatible. Which is partly the reason why they have been a hit in the jewellery industry (along with the fact that its a rare mineral).
Broad Optical Transparency
Optical transparency just means that Diamonds allow light rays to pass through. Due to the crystalline structure of Diamond, Light rays ranging from the ultraviolet band to the infrared band can pass through Diamond easily.
A crystal is a solid in which the atoms are arranged in a repetitive order of some basic structure. A material with a crystal structure is said to be crystalline.
Uses of Diamond
Diamond's unique properties allows it to be used in various industrial applications.
Jewellery
Diamond's hardness, rarity, durability, and lustre make it an attractive jewellery piece.
Industrial Tools
Only a material that is harder than the other can scratch or cut the other material. And there is no harder material than diamond, making it an excellent material for cutting tools like drill bits, milling tools, grinding wheels, saws, polishing tools, etc.
Heat Sinks
Heat sinks are heat exchangers which are used to cool down a component. Diamonds can conduct heat very efficiently and hence can heat up and cool down easily and rapidly. Therefore, they find application in heat sinks.
Diamond Windows
Not house windows, but windows in large laser machines, vacuum chambers, and X-ray machines. These windows have a very thin diamond membrane. This is a useful application since using Diamond in these membranes makes them durable and resistant to heat and abrasion.
Engraving
Diamond is used in the engraving of hard stones like granite and quartz.
Audio Equipment
Diamonds are used in record player needles and DJ equipment. Diamond is also believed to enhance audio as diamond domes can vibrate rapidly without deforming the audio waves and decreasing quality.
Medical Equipment
Diamonds are used in dental tools. Nano-diamonds are used in cancer treatment. Diamonds also have a potential use case in helping too make bionic eye implants to help the visually challenged.
Symbol of diamond in chemistry
The symbol for diamond in chemistry is C, since it is composed only of carbon atoms with a specific organization.
Diamond - Key takeaways
- Diamond is an allotrope of Carbon. It is naturally formed.
- The empirical formula of Diamond is C. It is very hard, the hardest material in the world.
- Carbon atoms have covalent bonds in the structure of Diamond. Each Carbon atom forms single bonds with 4 Carbon atoms. They are arranged in a tetrahedral geometry in the structure of Diamond.
- It has high thermal conductivity.
- It has high electrical resistivity. No free electrons → no charge flow → no current flow.
- Low chemical reactivity.
- High corrosion resistance.
- Low thermal expansion coefficient.
- Broad optical transparency. Allows light of wavelength ranging from ultraviolet to infra red to pass through itself.
- Low coefficient of friction.
- Diamond is used in Jewellery, Industrial tools like cutting tools, grinding tools, polishing tools etc., medical equipment, audio equipment, heat sinks. It's also used in engraving hard stones such as granite and quartz.
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