SF6 Lewis Structure: Drawings, Hybridization, Shape, Charges, Pair And Detailed Facts

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In this article, “SF6 lewis structure”, hybridization, geometry, formal charge along with some detailed explanations are discussed briefly.

SF6 is an inorganic colorless greenhouse non-flammable gas with an octahedral geometry in which one sulfur atom is attached with six fluorine atoms. It has an orthorhombic crystalline structure and hypervalent in nature. In SF6, the S-F single bond length is 156.4 pm.

Let’s focus on the structure, hybridization, formal charge and some relevant topics on sulfur hexafluoride.

How to draw lewis structure for SF6?

 Lewis structure known as electron dot structure was first introduced by eminent scientist Gilbert. N Lewis in the year of 1916 in his journal named as “The Atom and the Molecule”. Lewis structure has a great significance in Chemistry because number of bonds, nonbonding as well as bonding electrons, structure can be predicted from this structure.

There are some points should be kept in mind to draw lewis dot structure.

  • Valance electron has an important role in drawing lewis structure. Thus, no of electrons in valance shell should be counted first. In SF6, sulfur has six and fluorine has seven valance electrons respectively.
  • Octet rule (having eight electrons in valance shell to achieve noble gas electron configuration) should be applied if possible. For SF6, octet rule is only applicable for fluorine but not in sulfur. Fluorine needs one more electron to be octet filled up.
  • Number of covalent or ionic bonds should be calculated to know about the bonding electrons. After calculating bonding electrons, nonbonded electrons can be easily determined.

After maintaining all the above rules lewis dot structure is drawn (shown below).

sf6 lewis structure
SF6 Lewis Structure

 

SF6 Lewis Structure Shape

Shape of any molecule can be decided by the presence of different repulsion factor like bond pair-bond pair repulsion, lone pair-lone pair repulsion and lone pair-bond pair repulsion because the shape of the molecular species is deviated from its actual shape (geometry) due to the repulsion factor present in that molecule. The increasing order of this repulsion is-

Lone pair-lone pair repulsion > Lone pair-bond pair repulsion > bond pair-bond pair repulsion.

In SF6, sulfur has no lone pair, so lone pair-lone pair repulsion between the lone pair of central atom (sulfur) and substituent atom (fluorine) is absent. Thus, the geometry of SF6 is the shape of SF6 that is octahedral. No deviation is occurred from geometry to shape in SF6.

Sf6 shape
Shape of SF6.
Image Credit: Wikimedia Commons.

SF6 Lewis Structure Formal Charges

Lewis structure helps to determine the formal charge of each of the atom in the molecular species. Formal charge has a huge significance to decide if the molecule is a charged species or neutral in nature.

It can be calculated using the following formula-

  • Formal charge = Total number of valance electrons – number of electrons remain as nonbonded – (number of electrons involved in bond formation/2)
  •  Formal charge of sulfur = 6 – 0 – (12/2) = 0
  • Formal charge of each of the fluorine atom = 7 – 6 – (2/2) = 0

Valance electron of sulfur and fluorine is six and seven respectively. Number of nonbonding electrons for sulfur and fluorine is zero and six respectively.

SF6 Lewis Structure Lone Pairs

Number of lone pairs or nonbonded electrons can be determined from the total valance electron and number o electrons participate in bond formation.

  • Lone pair or nonbonded electron = Total number of valance electron – number of bonded electrons.
  • Nonbonded electrons on sulfur = 6 – 6 = 0
  • Nonbonded electrons on each of the fluorine atom = 7 – 1 = 6

In SF6 sulfur has total six valance electrons (3s2 3p4) and fluorine has seven outer most shell electrons (2s2 2p5).

Thus, central atom has no nonbonded electrons but substituent atom has 6 nonbonded electrons or three lone pairs in SF6 structure.

So, total nonbonded electrons in SF6 is {0 + ( 4×6)} = 24 or 12 lone pairs.

 SF6 Hybridization

Hybridization occurs or hybrid orbitals are formed due to mixing of two or more than two atomic orbitals for the purpose of chemical bonding and stability.

In SF6, the hybridization of central atom sulfur is sp3d2. Lewis structure also helps to determine the hybridization.

SF6 Hybridization
Hybridization of SF6

Sulfur has total six electrons in its valance shell. All the valance electrons are getting paired by the valence electron from each of the six fluorine and the hybridization arises as sp3d2. What we state in lewis structure point that sulfur has no electrons remain as nonbonded is proved through the hybridization image. There is six bond pairs and no lone pairs in SF6. In this hybridization one s orbital, three p orbital and two d orbitals of sulfur are involved. Due to absence of lone pair the actual geometry (octahedral) is shown by SF6. The <FSF bond angle is 900 in SF6 and the bond length of S-F bond is 156.4 pm.

SF6 Lewis Structure Octet Rule

Octet rule is very much known and one of the important rules in chemistry. But this rule is only applicable for main group element. Ionic or covalent molecule are also included in this octet rule.

Octet rule tells about the stability of any atom or molecule. It states that the valance shell of any atom should have eight electrons to achieve the nearest noble gas electron configuration.

This configuration gives any atom an extra stability and decreases the tendency to react with any other molecule like the noble gas. Noble gases have very much less tendency to take part in any reaction and known as inert molecule.

Let’s take an example of carbon dioxide. In CO2, carbon and oxygen have four and six valance electrons respectively. So, carbon needs four and oxygen needs six more electrons to be octet filled up. Thus, carbon and oxygen share their respective valance electrons with each other and help to have eight electrons in their valance shell. To achieve this goal, carbon forms double bond with each of the oxygen atom (O=C=O) and have a linear structure with a bond angle 1800.

In SF6 sulfur does not obey octet rule as it needs 12 more electron to have full filled valance shell electron configuration. But octet rule is applicable for fluorine because it needs one more electron to have total eight electrons in its outer most shell.

Frequently Asked Questions (FAQ)

Is SF6 reactive with water?

Answer: Sulfur atom is sterically hindered in SF6 due to presence of six fluorine atoms. For this hindrance, sulfur can not react with water, alkali hydroxides. Thus, SF6 is a kinetically inert molecule.

What are the intermolecular forces present in SF6 molecule?

Answer: The following intermolecular forces are present in SF6.

  • London dispersion force
  • Dipole-dipole interaction force
  • Hydrogen bonding.

Is SF6 reactive?

Answer: No, SF6 is basically an inert molecule with a lifetime 3200 years due to the huge steric hindrance on sulfur atom.

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