Draw the Lewis structure of carbon dioxide (CO2) and then determine if the molecule is polar or nonpolar.
The Correct Answer and Explanation is:
Lewis Structure of Carbon Dioxide (CO₂):
The carbon dioxide molecule consists of one carbon atom and two oxygen atoms. Here’s the correct Lewis structure:
mathematicaCopyEditO = C = O
Each line represents a pair of shared electrons (a covalent bond). Carbon makes two double bonds — one with each oxygen atom. Each oxygen atom has two lone pairs of electrons remaining.
Step-by-step Construction:
- Count total valence electrons:
- Carbon has 4 valence electrons.
- Each oxygen atom has 6 valence electrons.
- Total = 4 + (6 × 2) = 16 valence electrons.
- Determine the central atom:
- Carbon is less electronegative than oxygen and can form more bonds, so it goes in the center.
- Form bonds:
- Connect each oxygen to carbon with a double bond. This uses 8 electrons (4 per double bond).
- Distribute remaining electrons:
- Each oxygen gets 4 more electrons (2 lone pairs).
- Carbon already has 8 electrons (from the double bonds), satisfying the octet rule.
This structure uses all 16 valence electrons correctly.
Polarity of CO₂:
Carbon dioxide is a nonpolar molecule. Although each C=O bond is polar due to the difference in electronegativity between carbon and oxygen, the molecule is linear, meaning the two bond dipoles are equal in magnitude but opposite in direction. They cancel each other out.
Explanation:
- The molecular geometry of CO₂ is linear with a bond angle of 180 degrees.
- Since the molecule is symmetrical, the individual bond polarities cancel.
- The result is a molecule with no net dipole moment.
Even though the bonds themselves are polar, the overall shape causes the polarities to cancel, making CO₂ nonpolar.
Conclusion:
The Lewis structure of carbon dioxide shows a central carbon atom double bonded to two oxygen atoms. Due to its linear and symmetrical structure, CO₂ is a nonpolar molecule.
