In this article, “sf4 lewis structure”, hybridization, formal charge calculation shape of sulfur tetrafluoride are discussed briefly.
In SF4, sulfur is bonded with four fluorine atoms. Sulfur tetrafluoride is a see-saw structured molecule with sp3d hybridization. But the actual geometry of the molecule is trigonal bipyramidal. The deviation in shape is occurred due to the presence of lone pair of sulfur.
Main focus of this article is to discuss the shape of SF4 with some relevant topics.
How to draw lewis structure for SF4?
Lewis structure or lewis dot structure is very important in Chemistry for determining structure. Lewis structure helps to identify the bonded as well as nonbonded electrons with shape and geometry.
To draw the lewis structure of SF4 the following steps should be kept in mind.
- Valance electrons of each of the atom should be determined. Sulfur and fluorine have six and seven electrons respectively in their outer most shell.
- The next step is to calculate the number of electrons required to fill their respective valance shell. Sulfur needs twelve and fluorine needs one electron to fill their outer most shell because sulfur belongs to third group whereas fluorine belongs to the second group and the capability of having electron of second and third group is eight and eighteen respectively.
- The total numbers of covalent bonds will be calculated. In SF4, total four covalent bonds are present. Each bond is present between sulfur and one fluorine atom.
- Maintaining the above rules, SF4 lewis structure is drawn (Shown below).
SF4 Lewis Structure Shape
Shape of any molecule can be determined due to the presence of lone pair of central atom as well as the lone pair of substituent also. Because these lone pairs face repulsion with the nonbonded electrons of other atoms even with the electrons participate in bond formation. There is an increasing order in the magnitude of the electron-electron repulsion.
Lone pair-lone pair repulsion > lone pair-bond pair repulsion > bond pair-bond pair repulsion.
In SF4, sulfur has one lone pair of electron and each of the fluorine has five nonbonded electrons. These nonbonded electrons face lone pair- lone pair repulsion as well as lone-pair and bond pair-bond pair repulsion. Thus, the shape of sulfur tetra fluoride is deviated from its actual geometrical shape that is trigonal bipyramidal though the central atom (sulfur) is sp3d hybridized. The shape of SF4 is see-saw structure.
SF4 Lewis structure formal charges
Formal charge can be easily calculated from the lewis dot structure of that molecule. Formal charge helps to determine the overall charge of the molecular species. Because the charge of each and every atom is calculated from the formula of formal charge.
- 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 – 2 – (8/2) = 0
- Formal charge of each of the fluorine atom = 7 – 6 – (2/2) = 0
SF4 Lewis Structure Lone Pairs
In sulfur tetrafluoride, all of the participating atoms (sulfur and fluorine) have lone pairs. Lone pairs of any molecule can be calculated from total valence electron and number of electrons participate in covalent bond formation of that atom.
Lone pair or nonbonded electron = Total number of valance electron – number of bonded electrons.
In the structure of SF4, sulfur has total six valence electron (3s2 3p4) and among these electrons four electrons involve in bond formation. Thus, (6 – 4) = 2 electrons are left as nonbonding electrons.
Each of the fluorine has total seven electrons in its valence shell (2s2 2p5). Among those seven electrons, only one electron participates in single bond formation with sulfur. Thus, (7 – 1) = 6 electrons or 3 pair of electrons remain as nonbonded electron. The scenario is actually same for all of the four fluorine atoms.
In this molecule, sulfur is central atom and the hybridization of sulfur in SF4 is sp3d. To determine hybridization of any molecule valance electron and lewis structure of that molecule should be determined first.
Total outer most shell electron in SF4 is 34. Among these 34 electrons, six electrons come from sulfur and seven electrons come from each of the fluorine atom. From the electron counting we assume that sulfur needs twelve electrons to fill its valence shell.
Thy sp3d hybridization of SF4 is shown in the above picture. What we show in lewis structure is proved through the above image that sulfur has four bond pair and one lone pair. Sulfur uses its one 3s orbital, three 3p orbital and one 3d orbital for the sp3d hybridization. Due to inter electronic repulsion between the lone pair of sulfur and fluorine SF4 possesses see-saw structure. The actual geometry of SF4 should be trigonal bipyramidal but due to presence of bond pair lone pair repulsion the structure of SF4 is slightly deviated from its ideal shape. Bond length of S-F single bond is 164.6 pm and the bond angle < FSF is 101.60.
SF4 Lewis Structure Octet Rule
Octet rule is a very well known rule of chemistry that is applicable for main group element. This rule states that any atom should form bond (ionic or covalent) in such a way that it has total eight electrons in its outer most shell or valance shell.
Basically, this rule says about the stability of any molecular species or any atom. These eight electrons in valance shell or completely filled valance shell electron configuration can only be seen for noble gas molecule. When atoms are sort of eight electrons in their valance shell there is a tendency of that atom to reacts with another species. For this reason, noble gases are inert as they have full filled valance shell electron configuration. Thus, the tendency to react with another atom is very less for noble gas molecule.
This octet rule stabilizes any species. For example, in carbon dioxide, carbon (group IV) and oxygen (group VI) share their respective valance shell electron with each other and form two double bonds ( O=C=O).
In SF4, sulfur does not follow the octet rule as it requires eighteen electrons to fill its valance shell. Including bond pairs and lone pairs sulfur has total ten electrons. But fluorine obeys octet rule. Because it has total seven electrons in its valance shell. So, it needs one more electron to become octet filled up.
Frequently Asked Questions (FAQ)
Does sulfur tetrafluoride dissolve in water?
Answer: SF4 starts reaction with water when it is dissolved in water.
What are the uses of sulfur tetrafluoride?
Answer: SF4 is used mainly as fluorinating agent and it is also used as oil repellent and water making in chemical industry.