A crystal of diamond is a molecule of atoms in which each carbon atom is connected to four other carbon atoms by a strong covalent bond forming a regular tetrahedron shape.
In diamond, each carbon atom is linked by a covalent bond to four other carbon atoms surrounding it to give a three-dimensional covalently linked structure as shown below.
This strong bonding is responsible for the hardness of diamonds. Due to the absence of free electrons in this crystal structure, it does not conduct electricity
As the carbon atoms are held together firmly by covalent bonds, the diamond forms a very rigid structure.
The arrangement of carbon atoms in a diamond crystal is shown below:
