Hey guys, we all have doubts regarding the polarity of the molecules and also may wonder about how polarity is determined in the molecules. In this article, I will share my information regarding the polarity of SO3 (sulfur trioxide). If you also want to know whether SO3 is polar or nonpolar read this article till the end.
Is SO3 polar or nonpolar? SO3 is nonpolar and this is because of the trigonal planar shape of sulfur trioxide. Sulfur and oxygen have a difference in electronegativity due to which polarity arises in the S-O bond but the three S-O bonds lie at 120 degrees angle with each other cancels out the overall polarity and resulting in the formation of SO3 as a nonpolar molecule.
SO3 (Sulfur Trioxide) has a trigonal planar structure. It consists of one Sulfur atom surrounded by 3 Oxygen atoms symmetrically.
The atomic number of oxygen is 8, as a result, there are 6 electrons in the vacant shell of oxygen. Similarly, the atomic number of sulfur is 16 and there are 6 electrons in the vacant shell of Sulfur as well.
Basically, when we look at the lewis structure of the SO3, we see that 3 Oxygen atoms are spread around the single Sulfur atom and as a result of 2 lone pairs on each Oxygen atom they repel each other.
As a result, we found a trigonal planer molecule of SO3 (Sulfur trioxide). All of the oxygen atoms make symmetry around the Sulfur atom.
And one question that arises here is why Sulphur is in the center?
The atom with the lowest electronegativity always comes in the center and that atom whose electronegativity is least among all tends to make the highest number of bonds in that molecule.
This is why Sulphur comes in the center of SO3.
Similarly here Sulfur being the lowest electronegative atom in SO3, becomes the center atom.
Why is SO3 Non-Polar in nature?
After bonding in the SO3 molecule, the three pairs of Sulfur makes a double bond with the one pair of all three atoms of Oxygen surrounding the Sulfur atom.
The three bonds across the Sulfur and Oxygen atoms build the trigonal planar geometrical shape. The angle between the three bonds formed is 120 degrees.
The electronegativity of oxygen is 3.44 and the electronegativity of Sulfur is 2.58 due to which there is a difference in electronegativity and thus Sulfur oxygen bond becomes polar.
But the three bonds are at 120 degrees with each other and the overall polarity of SO3 gets canceled out.
Basically, the geometrical shape of the SO3 shows its nonpolar nature. The molecular structure of any molecule is an important factor to determine the polarity of that molecule.
Apart from the geometrical shape, a few other factors like lone pairs, the dipole moment of the molecule are also used to identify whether a molecule is polar or nonpolar.
If we talk about the properties of Sulfur trioxide (SO3), it is present in several types of molecular species and in the crystalline form.
SO3 is a strong oxidizing agent because Sulfur has a +6 oxidation state which is highest.
In the liquid state, it is colorless as well as odorless and in the solid-state, it can be seen as crystalline form.
In the gaseous state, it acts as a pollutant that can be checked by taking an example of acid rain. The rainwater mixed with Sulfur trioxide (SO3) is acid rain which is harmful to aquatic life as well as for humans.
How to determine polarity?
The molecule has many chemical dimensions associated with it that show the composition, geometrical structure, dipole moment, and bond formation.
The polarity of the molecule can also be determined with the help of such dimensions.
It is also important to know that the dipole moment of the SO3 is 0 D. The SI unit of dipole moment is debye which is denoted as ‘D’.
If the dipole moment of a molecule comes out to be zero, it means that the molecule is nonpolar.
Being a nonpolar molecule, the molecule shares equal charge distribution.
If the atoms involved in a molecule share equal charge distribution, its net dipole moment is zero whereas the molecule which has a net dipole moment has unequal charge distribution as they are polar in nature.
The Oxygen gas molecule O2 is an example of a nonpolar molecule. And the SO2 which has a bent shape is polar as it has some net dipole moment.
You can also read our other article on whether SO2 is polar or non-polar.
The dipole moment of a molecule is calculated as the product of bond length charge on each element
Apart from the dipole moment, the geometrical shape of the molecule also helps in determining the polarity of the molecule.
In the case of Sulfur trioxide (SO3), the trigonal planar shape having bonds at 120 degrees with each other that cancels out the polarity of each bond.
The bond formation of Sulfur trioxide depicts the symmetry of it which makes it nonpolar.
For better understanding, also check out an article written on SO3 Lewis Structure and its Molecular Geometry.
Polar and Nonpolar Molecules
Whenever bonding between two atoms occurs, one atom shares the electron of the other and vice versa.
In nonpolar molecules, the atoms involved in the molecule share an equal distribution of charge whereas, in polar molecules, the atoms do not share equal distribution of charge.
In those nonpolar cases, the electrons shared by both atoms in a covalent bond shifts towards the atom with a greater value of electronegativity.
And the atom with lesser electronegativity lets its bonded electron to shift towards the other atom with higher electronegativity.
Basically, the electronegativity of an atom is the measure of how strongly an atom can attract the electron towards its own side.
So, in polar cases, due to differences in electronegativity values, the bonded electrons are not in between both the atoms due to which polarity occurs in the molecule.
The dipole moment of a polar molecule comes out to be some positive value. Whereas the nonpolar molecules have the dipole moment value as 0 Debye.
As in the case of SO3, the dipole moment of each S-O bond cancels out.
Conclusion: Is SO3 Polar or Nonpolar?
SO3 is a nonpolar molecule because of the following factors:
Electronegativity: However, there is a difference in electronegativities of Sulfur and Oxygen atom in the S-O bond in the SO3 molecule. But due to symmetrical shape, the electronegativity difference gets canceled out.
Geometrical Shape: The geometrical shape of the SO3 is a trigonal planar where Sulfur is the center atom and the oxygen atom surrounds the sulfur atom at an angle of 120 degrees each.
Dipole moment: Due to the symmetrical shape of the bond and the trigonal planar shape of the molecule, the net dipole moment comes out as zero. However the dipole moment of the S-O bond is something, But the net dipole moment is 0 Debye.
I hope, I cleared your all doubts regarding the polarity of SO3 (sulfur trioxide molecule). If you have any questions let me know in the comment section and I’ll get back to you as soon as possible.