Understanding Hybridisation of SF₆: Sulfur Hexafluoride

Sulfur hexafluoride (SF₆) is also known as hexafluoro-λ6-sulphane. It is an inorganic compound and is a very stable gas. The gas is colourless and odourless. It’s a perfect example of sp³d² hybridisation in chemistry.

Let us understand how hybridisation happens in SF₆. Read on to learn how it leads to its bonding and molecular shape.

What is the Hybridisation of SF₆?

SF₆ consists of one sulfur atom and six fluorine atoms. Each fluorine atom is bonded to sulfur with single covalent bonds. In order to form these bonds, sulfur undergoes sp³d² hybridisation. Due to this hybridisation, this molecule has an octahedral molecular geometry.

Using the Hybridisation Formula

We can determine the hybridisation of Sulfur hexafluoride using the simple formula:

formula

Step-by-step calculation:

Valence electrons of central atom (S): 6
Number of monovalent atoms (F): 6
Negative charge: 0
Positive charge: 0

formula

Interpretation:

A hybridisation number of 6 corresponds to sp³d² hybridisation.
This explains the octahedral geometry of SF₆, where sulfur forms six S–F bonds with no lone pairs.

Breakdown of SF₆ Hybridisation

Sulfur hexafluoride is very stable because sulfur achieves an expanded octet with 12 valence electrons. It has 6 covalent single S–F bonds. In high-voltage equipment, it is a well-known electrical insulator.

Here is a complete understanding of its hybridisation.

Electronic Configuration of Sulfur

The atomic number of sulfur is 16.

The ground state of sulfur:

1s² 2s² 2p⁶ 3s² 3p⁴

Only two unpaired electrons → insufficient to form six bonds

Excited state configuration:

1s² 2s² 2p⁶ 3s¹ 3p³ 3d²

Six unpaired electrons → enough to form 6 bonds

Screenshot 2025-12-24 142407.png Alternative text

Ground state vs excited state orbital diagram

Formation of Hybrid Orbitals

sp³d² hybridisation occurs when 1 s orbital, 3 p and 2 d orbitals mix.

The result:

6 sp³d² hybrid orbitals on the sulfur atom
All the sp³d² hybrid orbitals used for σ bonding with fluorine atoms

Bond Formation in SF₆

Each sulfur atom uses:

All 6 sp³d² orbitals form a σ bond with fluorine
There are 0 π bonds present in SF₆

Result:

6 S–F σ bonds
Hybridisation type: sp³d²
Bond angle: 90°
Geometry: Octahedral

Geometry and bonding of SF₆

Details At A Glance

Property	Details
Molecule	Sulfur hexafluoride (SF₆)
Hybridisation	sp³d²
Geometry	Octahedral
Bond angle	90°
Bonding	6 σ bonds (S–F)
Unhybridised Orbitals	0 (hybridisation happens for all orbitals)
Sulfur valency satisfied?	Yes, by forming 6 bonds

Formal Charge in SF₆

To determine if the Lewis structure of SF₆ is stable, we calculate the formal charge on each atom using the formula:

Formal charge = Valence electrons − (Lone pair electrons + ½ × Bonding electrons)

Step-by-step for each atom:

Sulfur (S) – central atom

Valence electrons: 6
Lone pairs: 0
Bonding electrons: 12 (from six single bonds with F)

Formal charge = 6 − (0 + ½ × 12) = 6 − 6 = 0

Fluorine (F) – each

Valence electrons: 7
Lone pairs: 3
Bonding electrons: 2 (1 single bond with sulfur)

Formal charge = 7 − (6 + ½ × 2) = 7 − (6 + 1) = 7 − 7 = 0

Thus, all atoms in SF₆ carry zero formal charge, confirming that the Lewis structure is stable and correct.

Summing Up

The sulfur in SF₆ forms 6 single covalent bonds with fluorine. sp³d² hybridisation leads to an octahedral geometry with 90° bond angles. There are no π bonds between any atom in the molecule.

Frequently Asked Questions

Q1. Why does sulfur undergo hybridisation in SF₆?

To form 6 equivalent covalent bonds, sulfur promotes electrons and forms sp³d² hybrid orbitals.

Q2. How many σ and π bonds are present in SF₆?

There are 6 σ bonds and 0 π bonds in total.

Q3. What is the shape of SF₆?

Octahedral, due to sp³d² hybridisation.

Q4. Is SF₆ polar or non-polar?

SF₆ is non-polar, due to the cancelling of dipole, which is due to the octahedral arrangement of the molecule.

Q5. What are some uses of SF₆ in our daily lives?

SF₆ is used as an electrical insulator in high-voltage equipment and as a tracer in gas studies. It is also widely used as a protective gas in magnesium production.