Short Answer

sp hybridization is a type of hybridization in which one s orbital and one p orbital of an atom mix together to form two identical hybrid orbitals. These hybrid orbitals are arranged in a straight line with a bond angle of 180°, giving the molecule a linear shape.

Atoms that undergo sp hybridization usually form molecules with triple bonds or two double bonds, such as ethyne (C₂H₂) and carbon dioxide (CO₂). This type of hybridization helps explain the strong sigma bonds and linear geometry of these molecules.

Detailed Explanation :

sp Hybridization

sp hybridization is a concept used in valence bond theory to explain the bonding and geometry of molecules where an atom forms linear arrangements. In this type of hybridization, one s orbital and one p orbital from the same atom combine to form two new hybrid orbitals. These new orbitals are identical in shape, size, and energy. They orient themselves in a straight line, giving a bond angle of 180°. This arrangement reduces electron repulsion and creates a stable bonding structure.

sp hybridization often occurs in molecules where the central atom forms triple bonds or two double bonds, as seen in many organic and inorganic compounds. This hybridization helps us understand the directional bonding and strong sigma bonds present in these molecules.

How sp Hybridization Occurs

sp hybridization happens in three steps:

1. Mixing of Orbitals
   One s orbital and one p orbital combine to form two equivalent sp hybrid orbitals.
2. Formation of Hybrid Orbitals
   These two hybrid orbitals lie directly opposite each other, creating a linear shape.
3. Remaining p Orbitals
   Since a p subshell has three p orbitals, and only one mixes in sp hybridization, two p orbitals remain unhybridized.
   These unhybridized p orbitals form pi (π) bonds in double and triple bonds.

This mixing of orbitals allows atoms to form strong and directional sigma bonds.

Characteristics of sp Hybridization

sp hybridization has several unique characteristics:

1. Linear Geometry

The two sp hybrid orbitals align at 180°, giving the molecule a linear shape.

Examples of linear molecules:

• CO₂ (O═C═O)
• C₂H₂ (H–C≡C–H)

2. Formation of Sigma Bonds

Each sp hybrid orbital forms a sigma bond by overlapping with orbitals of other atoms.
Sigma bonds formed through sp hybridization are very strong due to effective overlap.

3. Formation of Pi Bonds

The remaining two unhybridized p orbitals form pi bonds.
These pi bonds:

• Create double or triple bonds
• Restrict rotation
• Increase bond strength

For example:
In ethyne (C₂H₂), carbon forms one sigma bond and two pi bonds.

4. High Bond Strength

Because sp orbitals have more s-character (50%), the electrons are held closer to the nucleus.
This results in:

• Stronger sigma bonds
• Shorter bond lengths
• Higher stability

5. 50% s-character and 50% p-character

The mixing of one s orbital and one p orbital means each sp hybrid orbital is:

• 50% s
• 50% p

More s-character means greater strength and stability of bonds.

Examples of sp Hybridization

1. Ethyne (C₂H₂)

Each carbon atom forms:

• Two sp hybrid orbitals (one bond with H, one sigma bond with C)
• Two unhybridized p orbitals that form two pi bonds

This creates a triple bond between the two carbon atoms.

2. Carbon Dioxide (CO₂)

The carbon atom undergoes sp hybridization, forming two sigma bonds with oxygen atoms.
Each oxygen then forms a pi bond, creating two double bonds.

The molecule becomes linear with a bond angle of 180°.

3. BeCl₂

Beryllium forms two sigma bonds with chlorine atoms using sp hybrid orbitals.
This gives a linear structure.

Importance of sp Hybridization

sp hybridization is important because it helps explain:

• Linear molecular shapes
• Formation of triple bonds
• Formation of double bonds
• Strong sigma bonds
• Bond lengths and strengths
• Restricted rotation in multiple bonds

It is especially important in organic chemistry, where molecules like alkynes (containing triple bonds) depend on this hybridization for their structure and reactivity.

Comparison with Other Hybridizations

Type	Number of Hybrid Orbitals	Bond Angle	Shape
sp	2	180°	Linear
sp²	3	120°	Trigonal planar
sp³	4	109.5°	Tetrahedral

This shows that sp hybridization produces the simplest and straightest shape.

Conclusion

sp hybridization occurs when one s and one p orbital mix to form two identical hybrid orbitals arranged linearly at 180°. This hybridization explains why molecules like CO₂ and C₂H₂ have straight-line shapes and strong sigma bonds. The remaining unhybridized p orbitals form pi bonds, creating double or triple bonds. sp hybridization is essential for understanding molecular geometry, bonding strength, and behaviour in many important chemical compounds.