Short Answer

d²sp³ hybridization is a type of hybridization in which two d orbitals, one s orbital, and three p orbitals mix to form six identical hybrid orbitals. These orbitals arrange themselves in an octahedral geometry, where six bonds or electron pairs are positioned at 90° angles around the central atom.

This hybridization is commonly seen in molecules or ions where the central atom forms six sigma bonds or has six electron domains, such as sulfur hexafluoride (SF₆) and hexafluorophosphate ion (PF₆⁻). It explains how certain elements expand their octet and form stable structures with six surrounding atoms.

Detailed Explanation :

d²sp³ Hybridization

d²sp³ hybridization is an advanced hybridization model used to explain the bonding and structure of molecules that contain six electron pairs around a central atom. In this hybridization, two d orbitals, one s orbital, and three p orbitals combine to form six hybrid orbitals, all of equal energy, shape, and direction. These hybrid orbitals arrange themselves at 90° angles, forming an octahedral geometry.

This type of hybridization occurs only in atoms from the third period or higher, such as sulfur, phosphorus, chlorine, bromine, xenon, etc., because these atoms have accessible d orbitals. d²sp³ hybridization helps explain why such atoms can form compounds with more than four bonds and expand their octet beyond eight electrons.

How d²sp³ Hybridization Occurs

The process of d²sp³ hybridization involves several steps:

1. Availability of d Orbitals

For hybridization to occur, the central atom must have vacant d orbitals.
This is why elements from period 3 onward can undergo d²sp³ hybridization, while period 1 and 2 elements cannot.

2. Mixing of Orbitals

• Two d orbitals
• One s orbital
• Three p orbitals

These five orbitals mix together to form six hybrid orbitals.

3. Formation of Hybrid Orbitals

The hybrid orbitals formed are identical in:

• Shape
• Energy
• Orientation

They are arranged in an octahedral pattern to minimize electron repulsion.

4. Bond Formation

Each hybrid orbital overlaps with orbitals from surrounding atoms to form six sigma bonds, or it may hold a lone pair if present.

Geometry in d²sp³ Hybridization

The geometry of this hybridization is octahedral, meaning:

• Six positions around the central atom
• Bond angle = 90°
• All positions are equivalent

Examples of perfect octahedral molecules:

• SF₆
• PF₆⁻

If lone pairs occupy some orbitals, the shape changes while the electron geometry remains octahedral.

Shapes derived from octahedral arrangement:

• Square pyramidal → one lone pair
• Square planar → two lone pairs (e.g., XeF₄)

Examples of d²sp³ Hybridization

1. Sulfur Hexafluoride (SF₆)

• Sulfur undergoes d²sp³ hybridization.
• Forms six S–F sigma bonds.
• Perfect octahedral shape.

2. Hexafluorophosphate Ion (PF₆⁻)

• Phosphorus forms six sigma bonds with fluorine.
• Octahedral geometry with no lone pairs.

3. Xenon Tetrafluoride (XeF₄)

• Xenon uses d²sp³ hybrid orbitals to form four sigma bonds.
• Two hybrid orbitals contain lone pairs.
• Molecular shape = square planar.

4. Bromine Pentafluoride (BrF₅)

• One lone pair + five bonds around bromine.
• Electron geometry is octahedral even though molecular shape is square pyramidal.

These examples show that shapes may vary, but the electron geometry remains based on d²sp³ hybridization.

Characteristics of d²sp³ Hybridization

1. Expanded Octet

The central atom can have up to twelve electrons in its valence shell.
This is possible only because d orbitals are available.

2. Formation of Six Strong Sigma Bonds

Hybrid orbitals point toward the corners of an octahedron, creating very strong directional sigma bonds.

3. Equal Energy Orbitals

All six hybrid orbitals have the same energy, allowing uniform bonding.

4. Suitable for Highly Symmetric Structures

Compounds like SF₆ are extremely stable because of symmetrical electron distribution.

5. Presence of Lone Pairs

Even if lone pairs occupy some hybrid orbitals:

• Electron geometry stays octahedral
• Molecular geometry may change

Example:
XeF₄ → square planar
BrF₅ → square pyramidal

Importance of d²sp³ Hybridization

d²sp³ hybridization is important because it explains:

• How atoms form six sigma bonds
• Why molecules have octahedral structures
• How elements expand their valence shells
• Differences between electron geometry and molecular geometry
• Stability of molecules with high coordination numbers
• Bond lengths and angles in larger molecules

It also helps in understanding complex ions and coordination compounds in inorganic chemistry.

Conclusion

d²sp³ hybridization is a process in which two d orbitals, one s orbital, and three p orbitals combine to form six identical hybrid orbitals arranged in an octahedral geometry. This type of hybridization allows atoms to form six sigma bonds or hold lone pairs while maintaining a symmetrical electron arrangement. It is crucial for understanding bonding in molecules like SF₆, PF₆⁻, XeF₄, and BrF₅. Overall, d²sp³ hybridization explains expanded octets, strong sigma bonding, and octahedral shapes in many advanced chemical structures.