Final answer:
Carbon dioxide (CO₂) is nonpolar due to its linear molecular geometry, which allows the equal but opposite dipoles from the carbon to each oxygen to cancel out, leaving no overall dipole moment.
Step-by-step explanation:
The substance carbon dioxide (CO₂) is nonpolar. Carbon dioxide is a linear molecule comprised of a carbon atom bonded to two oxygen atoms. Despite the polar bonds between the carbon and oxygen atoms due to oxygen's higher electronegativity, the molecule's linearity causes these dipole moments to be of equal strength but oriented oppositely, resulting in their cancellation. This lack of a net dipole moment ensures that CO₂ remains a nonpolar molecule.
The molecular geometry, specifically the linear arrangement in carbon dioxide, is essential in determining the molecule's polarity. For instance, contrast this with water (H₂O), which has bent geometry; therefore, the dipole moments do not cancel, leading to a polar molecule. Understanding the VSEPR (Valence Shell Electron Pair Repulsion) theory helps in explaining why the shape of the CO₂ molecule is linear and why this geometry results in a nonpolar character.