Octahedral

Definition

Octahedral refers to a molecular geometry where a central atom is surrounded by six other atoms or groups of atoms, arranged at the vertices of an octahedron. This geometry arises from the hybridization of orbitals and is characterized by bond angles of 90 degrees and 180 degrees, reflecting the symmetrical arrangement of atoms around the central atom.

5 Must Know Facts For Your Next Test

1. An octahedral geometry occurs when a molecule has six regions of electron density around the central atom, which could be six bonded pairs or a combination of bonded pairs and lone pairs.
2. Common examples of octahedral molecules include sulfur hexafluoride (SF6) and xenon difluoride (XeF2), showcasing how the octahedral shape accommodates various bonding scenarios.
3. In octahedral complexes, the arrangement allows for optimal overlap of hybrid orbitals with the p orbitals of surrounding atoms, leading to strong sigma bonds.
4. The presence of lone pairs can alter ideal octahedral geometry, leading to shapes like square pyramidal or square planar if one or two positions are occupied by lone pairs instead of bonded atoms.
5. The concept of octahedral geometry is important in coordination chemistry, as many metal complexes exhibit this structure due to their ability to form coordinate covalent bonds.

Review Questions

• How does the octahedral geometry relate to the hybridization of atomic orbitals?
  • In an octahedral geometry, the central atom typically undergoes sp^3d^2 hybridization, where one s orbital, three p orbitals, and two d orbitals combine to form six equivalent hybrid orbitals. These orbitals arrange themselves in space to minimize electron pair repulsion, resulting in the characteristic 90-degree and 180-degree bond angles associated with octahedral shapes. This hybridization explains why octahedral molecules maintain their specific geometric configuration.
• What are the differences between an octahedral and tetrahedral molecular geometry, particularly regarding bond angles and electron arrangements?
  • Octahedral geometry features six regions of electron density around a central atom, leading to bond angles of 90 degrees and 180 degrees. In contrast, tetrahedral geometry involves four regions of electron density, resulting in bond angles of approximately 109.5 degrees. The difference in spatial arrangement affects how these geometries interact with surrounding atoms and influences the overall shape and reactivity of the molecules.
• Evaluate the impact of lone pairs on the ideal octahedral geometry and provide examples of altered geometries that can arise.
  • Lone pairs significantly affect the ideal octahedral geometry by occupying space around the central atom, altering bond angles and overall shape. For instance, if one lone pair is present in an octahedral arrangement, it can lead to a square pyramidal geometry due to repulsion from bonded pairs. If two lone pairs occupy opposite positions, the resulting shape may be square planar. These alterations highlight how lone pairs influence molecular behavior and properties in coordination compounds.

Related terms

Hybridization: The process of mixing atomic orbitals to create new hybrid orbitals suitable for bonding, leading to specific molecular geometries.

Tetrahedral: A molecular geometry where a central atom is bonded to four other atoms, forming a shape with bond angles of approximately 109.5 degrees, similar to an octahedron but with fewer bonded atoms.

Trigonal Bipyramidal: A molecular geometry formed when a central atom is surrounded by five other atoms, resulting in two different bond angles: 90 degrees and 120 degrees.