Chem Explorers

The Paradox of Ethyne: A Nonpolar Molecule with Polar Bonds

When it comes to chemistry, understanding molecular polarity is essential for understanding many chemical reactions. One molecule, in particular, that is interesting to study is ethyne (C2H2).

Ethyne has a unique structure made up of two carbon atoms and two hydrogen atoms but what makes it different from other molecules? In this article, we will dive into the structure of ethyne and compare it to other nonpolar molecules.

Polarity of Ethyne:

The key to understanding the polarity of ethyne is to first understand its Lewis structure. A Lewis structure is a model that shows how atoms are bonded together within a molecule.

In ethyne, each carbon atom is bonded to one hydrogen atom and to the other carbon atom with a triple bond. This means that each carbon atom has one single bond and one triple bond.

Carbon and hydrogen atoms have different electronegativity values, which determines how evenly they share electrons. Electronegativity is the ability of an atom to attract electrons towards itself.

Carbon has an electronegativity of 2.55, and hydrogen has an electronegativity of 2.20. Therefore, the electrons in the carbon-hydrogen bonds are more attracted to carbon, creating polar covalent bonds.

However, due to the linear geometry of the molecule, the polar bonds cancel each other out, making the molecule nonpolar. Factors Determining Polarity:

Factors that determine the polarity of a molecule include the electronegativity difference between atoms, the shape of the molecule, and the distribution of charges.

As mentioned previously, the electronegativity difference between carbon and hydrogen in ethyne causes polarity, but the canceling out of the polar bonds due to linear geometry makes the molecule nonpolar. Another factor that determines polarity is the shape of the molecule.

Ethyne has a linear geometry, meaning the atoms align in a straight line. This symmetrical arrangement and even distribution of electrons means that the molecule has no dipole moment, making it nonpolar.

Lastly, the distribution of charges within the molecule affects polarity. Molecules with an even distribution of charges are nonpolar, while those with an uneven distribution are polar.

Ethyne has an even distribution of charges, meaning it is nonpolar. Comparison with Other Nonpolar Molecules:

Another molecule that is similar in structure and nonpolar is carbon disulfide (CS2).

Carbon disulfide is made up of one central carbon atom and two sulfur atoms, each with a double bond. The shape of the molecule is linear, just like ethyne, and the electronegativities of carbon and sulfur are similar, making it nonpolar.

The difference between ethyne and carbon disulfide lies in the electronegativity of the atoms used to build the molecule. In carbon disulfide, the sulfur atoms have an electronegativity of 2.58, making them slightly more electronegative than the carbon atom’s electronegativity of 2.55.

This means that the shared electrons between sulfur and carbon are slightly more attracted to sulfur, creating polar covalent bonds. However, the linear shape of the molecule and the even distribution of charges make it nonpolar.


Understanding the polarity of molecules is crucial in understanding many chemical reactions. Ethyne, with its linear geometry and even distribution of electrons, is a nonpolar molecule despite the polar covalent bonds.

Carbon disulfide, with a similar linear geometry but slightly different electronegativity values, is also a nonpolar molecule. Being familiar with the factors that determine polarity will help in identifying nonpolar molecules, which are vital for many industrial and biological applications.In the previous section, we have learned that ethyne is a nonpolar molecule that defies conventional logic.

Despite the presence of polar covalent bonds, it does not exhibit any net dipole moment, making it nonpolar. In this article, we will go into detail about the factors that govern the polarity of ethyne and the applications it has in various fields.

Detailed Discussion:

Ethyne’s Lewis structure shows that it is made up of two carbon atoms and two hydrogen atoms. The carbon-carbon triple bond dominates the structure, and this means that it has six valence electrons – two in the single bond and four in the triple bond.

The Lewis structure also allows us to determine the shape of the ethyne molecule, which is linear and symmetrical. The linear shape of the molecule causes any opposing forces to cancel each other out, resulting in a net dipole moment of zero.

To better understand this nonpolarity, we need to examine the factors that contribute to a molecule’s polarity. The most important factor is electronegativity, which is the ability of an atom to attract electrons within a chemical bond.

Electronegativity values can range from 0 to 4.0, and as the difference in electronegativity between two atoms increases, so does their bond’s polarity. Carbon and hydrogen atoms share covalent bonds that have polarities because of their differing electronegativity values.

Carbon has an electronegativity value of 2.55, while hydrogen’s value is 2.20. Therefore, carbon has a stronger pull on the shared electrons than hydrogen does, resulting in a slight polarity for the C-H bonds.

However, when we consider the entire molecule as a whole, the linear structure creates a scenario where the opposing polar bonds cancel each other out. As a result, ethyne has no net dipole moment and is a nonpolar molecule.

Ethyne’s nonpolarity has practical applications in industries such as welding, cutting, and brazing. Ethyne mixed with oxygen produces an intensely hot flame that can melt metal.

Its high energy output makes it useful for cutting and welding. The use of ethyne in these applications is possible due to the molecule’s nonpolarity, which allows for better combustion and easier control over the flame.

Moreover, ethyne has a unique set of physical and chemical properties due to its high reactivity attributed to the carbon triple bond’s strength. Such reactivity is exceptional and can be harnessed for high-end applications.

The hydrocarbons derived from ethyne or acetylene are essential precursors for the fabrication of commercial chemicals such as resins, plastics industry, and synthetic rubber materials. The ability to manipulate ethyne’s reactivity is instrumental in developing new industrial applications in the pharmaceutical, biotech, and polymer industries.


In conclusion, the nonpolarity of ethyne is the result of a complex interplay between the polar covalent bonds of C-H and C-C and the linear symmetry of the molecule, which creates an even distribution of charge. This nonpolarity has various applications in different industries, such as cutting and welding, and is an important precursor for many commercial chemicals.

Understanding the polarity of molecules is critical, and further research on both the physical and chemical properties of ethyne can yield remarkable discoveries. In summary, the article has explored the polarity of ethyne, a nonpolar molecule despite the presence of polar covalent bonds.

The nonpolarity is due to both the electronegativity difference and the symmetry of the molecule, which cancels out any opposing forces. We have also discussed the practical applications of ethyne in various industries such as welding and cutting, and its significance in the production of chemicals.

Understanding the polarity of molecules is essential, and ethyne is a prime example of its complexity. Ultimately, the research into ethyne’s unique properties can remarkably benefit various industries.


Q: Why is ethyne considered a nonpolar molecule? A: The linear geometry of the molecule and the even distribution of charges cancel out the opposing polar covalent bonds, resulting in a net dipole moment of zero.

Q: What are the applications of ethyne in industries? A: Ethyne is used in industries like welding and cutting due to its high-temperature combustion, which is made more efficient by the molecule’s nonpolarity.

Q: How is ethyne significant to the production of commercial chemicals? A: Ethyne is a crucial precursor for many commercial chemicals used in the plastic, rubber materials, and synthetic resin industries.

Q: Why is it essential to understand the polarity of molecules? A: Understanding a molecule’s polarity is crucial in explaining various chemical reactions and has practical importance in many industries such as medicine, engineering, and materials science.

Q: Can ethyne provide breakthroughs in other research areas? A: Ethyne’s unique properties and high reactivity can be exploited for future research in the biotech, pharmaceutical, and polymer industries.

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