Hexagonal Close Packing – Structure and hcp Structure Unit Cell

Definition and Explanation of Hexagonal Close Packing

The hexagonal close packing (HCP) is a stacking arrangement of particles in which each particle is surrounded by six other particles in a close-packed hexagonal lattice. The HCP is the densest possible packing of spheres in a three-dimensional space.

The HCP can be described by the following three parameters:

• The number of particles per layer, n
• The number of layers, L
• The particle diameter, d

The number of particles per layer, n, is the number of particles in a layer divided by the number of layers. For the HCP, n = 6.

The number of layers, L, is the total number of layers in the stack. The particle diameter, d, is the diameter of a sphere that will fit in the hexagonal lattice.

Structure bonding and reactivity of carbon

• The carbon atom has six electrons in its outer shell. It can share these electrons with other atoms to form covalent bonds. Carbon atoms can also form ionic bonds by losing or gaining electrons.
• Carbon is a very versatile atom and can form a variety of molecules. It is the basis of all organic molecules and can form chains, rings and networks. Carbon is also very reactive and can form compounds with most other elements.
• Carbon is the basic building block of all organic molecules and is the most important element in terms of its ability to form strong bonds with other atoms. The strength of the bonds that carbon can form is due to the fact that it has four valence electrons in its outermost shell. This gives carbon the ability to form four covalent bonds with other atoms.
• The most common bond that carbon forms is the single bond. In a single bond, two electrons shared between the two atoms. The carbon-carbon bond is the strongest type of single bond and found in all organic molecules. The next strongest type of bond is the double bond, which involves the sharing of four electrons between the two atoms. The carbon-oxygen double bond is the strongest type of double bond and found in many organic molecules. The weakest type of bond is the triple bond, which involves the sharing of six electrons between the two atoms. The carbon-nitrogen bond is the weakest type of triple bond and found in very few organic molecules.
• The reactivity of carbon is due to the fact that it can form strong bonds with other atoms. The most common reaction that carbon undergoes is combustion, which is the reaction of carbon with oxygen to form carbon dioxide. Carbon can also react with other elements to form compounds known as carbides. The most common carbide is calcium carbide, which used in the production of acetylene.

Hcp Structure Unit Cell

The hexagonal close-packed (hcp) structure is a repeating unit cell that has six atoms arranged in a hexagonal pattern. Therefore the atoms arranged in a close-packed manner, with each atom occupying a shared vertex of the hexagon and one-third of an edge. This results in a dense packing of atoms, with each atom occupying a space of 0.236 square nanometers.