closest packing

(noun)

A phenomenon resulting in the crystal structure of atoms/molecules having their component parts as near to each other as possible.

Related Terms

Examples of closest packing in the following topics:

  • Crystal Structure: Closest Packing

    • Closest packing refers to the most efficient way to arrange atoms in a crystalline unit cells.
    • The most efficient conformation of atomic spheres within a unit cell is known as the closest packing formation.
    • Because the third layer is aligned the same way as the first, this configuration is referred to as "ABA" and results in hexagonal closest packing (HCP).
    • This configuration is referred to as "ABC" and results in cubic closest packing (CCP).
    • Two methods of packing spheres into a unit cell yield the most common closest packing conformations: CCP and HCP.

  • Crystal Structure: Packing Spheres

    • These spheres are packed into unit cells.

  • Brønsted Acid Additions

    • Of all the reagents discussed here, these strong acid additions (E = H in the following equation) come closest to proceeding by the proposed two-step mechanism in which a discrete carbocation intermediate is generated in the first step.

  • Properties of Alkenes

    • The melting and boiling points of alkenes are determined by the regularity of the packing, or the closeness, of these molecules.
    • Alkene isomers that can achieve more regular packing have higher melting and boiling points than molecules with the same molecular formula but weaker dispersion forces.

  • Carbides

    • They are formed so that the carbon atoms fit into octahedral interstices in a close-packed metal lattice when the metal atom's radius is greater than ~135 pm.
    • When the metal atoms are cubic-close-packed (ccp), then filling all of the octahedral interstices with carbon achieves 1:1 stoichiometry with the rock-salt structure.
    • When the metal atoms are hexagonal-close-packed, (hcp), since the octahedral interstices lie directly opposite each other on either side of the layer of metal atoms, filling only one of these with carbon achieves 2:1 stoichiometry.
    • As a result of the packing, they are quite stable and have very high melting points and low electrical resistance.

  • Boiling & Melting Points

    • This reflects the fact that spheres can pack together more closely than other shapes.
    • Even-membered chains pack together in a uniform fashion more compactly than do odd-membered chains.

  • General Properties of Metals

    • Metals typically consist of close-packed atoms, meaning that the atoms are arranged like closely packed spheres.

  • Standard Entropy

    • For the noble gases, this is a direct reflection of the principle that translational quantum states are more closely packed in heavier molecules, allowing them to be occupied.
    • The entropies of solid elements are strongly influenced by the type of atom packing in the solid.

  • Metallic Crystals

    • Atoms in metals are arranged like closely-packed spheres, and two packing patterns are particularly common: body-centered cubic, wherein each metal is surrounded by eight equivalent metals, and face-centered cubic, in which the metals are surrounded by six neighboring atoms.
    • The high density of most metals is due to the tightly packed crystal lattice of the metallic structure.

  • Ionic Crystals

    • These are known as close-packed structures, and there are several kinds of them.
    • In ionic solids of even the simplest 1:1 stoichiometry, the positive and negative ions usually differ so much in size that packing is often much less efficient.