Hence the dipole moment is not canceled, which makes the molecule polar.
And as fluorine atoms are more electronegative than the sulfur atom, it results in uneven distribution of the charge. Here, one lone pair on the central sulfur atom and four bonding pairs of electrons leads to the asymmetric distribution of electrons on the central atom.Īlso, as the shape of the molecule is like a see-saw, two fluorine atoms can cancel out each other’s dipole moment, but the rest two can’t due to the electrons’ arrangement.
Once we know the Lewis structure and molecular geometry of the given compound, it becomes easier to depict the molecule’s polarity. At the same time, each fluorine atom will have three lone pairs. Hence, the central atom, sulfur, will have one lone pair of electrons and four bonding pairs of electrons in the Lewis structure of SF4. In contrast, the central atom will have two valence electrons and four bonds. Each fluorine atom will have three pairs of 6 valence electrons ( shown as dots) on the atom, along with one bond with sulfur.
All the fluorine atoms have six valence electrons, and the central atom has two valence electrons.ĭraw lines between S and F to show bonds and for lone pairs of electrons, use dots. So now, eight valence electrons are used, reducing the number of valence electrons from 34 to 24. Every fluorine atom will form a bond with the central atom, which means there will be four bonds in the molecule structure using up four valence electrons of fluorine atoms and 4 electrons of the sulfur atom. Sulfur will be the central atom in this molecule as it is the least electronegative, with four fluorine atoms forming bonds on the sides of this central atom. Now that we know the total number of valence electrons, it would become easy for us to understand the bond formation between the atoms and the complete arrangement of the molecule too. Total number of valence electrons in SF4 = number of valence electrons in sulfur + number of valence electrons in fluorine ( as there are four fluorine atoms, we have to consider valence electrons of all atoms) To know the total valence electrons of this compound, we need to know the valence electrons of both the atoms individually. The valence electrons that participate in forming bonds are called bonding pairs of electrons, whereas the electrons that do not participate or form any bonds are called nonbonding pairs of electrons or lone pairs.Īnd to draw the Lewis structure of SF4, we first need to know the total number of valence electrons in this molecule.Īs one can probably see, there is one sulfur atom in this compound and four fluorine atoms. The bonds formed between two atoms are depicted using lines, whereas the valence electrons not forming any bonds are shown by dots. Lewis structure is a pictorial representation of the bonds and valence electrons in the molecule. Hence, SF4 has a trigonal bipyramidal molecular geometry. The electrons follow this pattern of arrangement following the VSEPR rule to minimize the repulsion forces between the lone pairs of electrons to maximize the molecule’s stability. As there is one lone pair on the central atom, it repels the bonding pair of electrons, which tweaks the shape a little bit and makes it appear like a see-saw. Here two fluorine atoms forming bonds with the sulfur atom are on the equatorial positions, and the rest two are on the axial positions. Molecules having a molecular formula of AX4E have trigonal bipyramidal molecular geometry.
Here there is one sulfur atom and four fluorine atoms in the compound, which makes it similar to the molecular formula of AX4E. A molecular formula helps to know the exact number and type of atoms present in the given compound. It is easy to understand the molecular geometry of a given molecule by using the molecular formula or VSEPR model.
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