Which of the following substances is typically not a polar molecule?

The correct answer highlights carbon dioxide's unique molecular geometry and electronegativity considerations that contribute to its nonpolar characteristics.

Carbon dioxide (CO₂) is a linear molecule where the carbon atom is double bonded to two oxygen atoms. Although oxygen is more electronegative than carbon, which creates polar bonds, the linear shape of the molecule allows for the bond dipoles to cancel each other out. As a result, the overall molecule does not have a net dipole moment, classifying it as nonpolar.

In contrast, water, ammonia, and hydrogen chloride exhibit polar characteristics due to their geometries and the presence of electronegative atoms. Water's bent shape leads to an unequal distribution of charge, resulting in a significant dipole moment. Ammonia, with its trigonal pyramidal shape, also has an unequal distribution of charge thanks to the nitrogen atom's higher electronegativity compared to hydrogen. Hydrogen chloride features a polar bond due to the electronegativity difference between hydrogen and chlorine, leading to a net dipole moment in the molecule.

Understanding these molecular shapes and electronegativities is crucial for determining whether a molecule is polar or nonpolar, making carbon dioxide a prime example of a nonpolar molecule in this