Ethyne or Acetylene is an organic compound used in the synthesis of other hydrocarbon compounds as well as for cutting and welding work. It has a chemical formula of C2H2 and is made up of two atoms of Carbon and two atoms of Hydrogen. To determine its polarity one has to look at its Lewis Structure first to understand the molecular geometry and the shape of the molecule.
In the Lewis structure of C2H2, Carbon atoms take the central position, and the Hydrogen atoms are arranged around it. Both Carbon atoms share one valence electron with one Hydrogen atom by forming a single bond. And to complete their octets, both these atoms share their remaining three valence electrons in the outer shell by forming a triple bond. The bond angles in the molecule are 180°, and there are no lone pairs of electrons in this structure.
So if you look at the Lewis Structure of C2H2, it is quite symmetric as both these carbon atoms form single bonds with Hydrogen atoms.
Is C2H2 a polar or nonpolar molecule?
C2H2 or Ethyne is a nonpolar molecule. It has a symmetric distribution of electrons and a linear geometry. The polarity of any molecule depends on the following factors:
- The difference in electronegativities of atoms
- The shape of the molecule
- Dipole moment
- Distribution of charges
C2H2 is made up of two types of atoms: Carbon and Hydrogen. The Carbon atom has an electronegativity of 2.55 and Hydrogen has an electronegativity value of 2.20
The difference of their electronegativities is almost 0.35, which is lesser than 0.4 and hence C-H bonds are nonpolar. And as the difference of electronegativities is not that high, there will be nearly no to zero dipole moment in this molecule.
The atoms are arranged in a linear geometry, which means the distribution is even on both the sides so even if there is a dipole moment, it will get nullified due to the opposite directions.
As the C-H bonds are nonpolar there will be no net dipole moment in this molecule. And as there is no net dipole moment, there are no poles in this molecule.
Now when we look at the distribution of charges in this molecule, it is evenly distributed. There are no positively charged regions and negatively charged regions in this molecule. This even distribution of the charges also makes this molecule a nonpolar molecule.
Generally, the molecules that have linear geometry and no lone pairs of electrons are nonpolar. CS2 or Carbon Disulfide is also one of the molecules that have linear geometry and is nonpolar. Apart from that, the compounds with polar covalent bonds are polar due to the uneven distribution of charges in the molecule.
Ethyne or Acetylene is a nonpolar molecule as there are no unshared pairs of electrons and uneven charge distribution in the molecule. It has a linear geometry and no net dipole moment.