Chemistry
Chemistry
Problem
Carbon dioxide, CO₂, and sulfur dioxide, SO₂, are both triatomic molecules in which the central atom is bonded to two oxygen atoms. Despite this similarity, the experimentally-determined O–X–O bond angles differ markedly. (a) Draw complete Lewis electron-dot diagrams for CO₂ and SO₂, showing all lone pairs and, where appropriate, resonance structures. (b) For each central atom, state the total number of regions of electron density (bonding plus lone-pair regions) and specify how many of those regions are lone pairs. (c) Using the information from part (b), explain why the overall geometric arrangement of atoms in CO₂ is linear whereas in SO₂ it is bent. In your explanation, explicitly address the role of lone pairs and multiple bonds. (d) Predict which of the two molecules has the larger molecular dipole moment. Justify your answer based on molecular geometry and bond polarity. (a) Lewis electron-dot diagrams (b) Regions of electron density (c) Explanation of differing shapes (d) Prediction and justification of relative dipole momentsIntuitive explanation
The key to understanding these molecules is recognizing that VSEPR theory depends not just on what atoms are bonded, but on all regions of electron density around the central atom—including lone pairs. Carbon and sulfur have different numbers of valence electrons and different abilities to expand their octets, so they end up with different electron geometries. Once you know how many lone pairs surround each central atom, you can predict whether the molecule bends or stays linear, and that geometry directly determines whether the bond dipoles cancel out or add up to create a net molecular dipole.
Intuitive explanation
The key to understanding these molecules is recognizing that VSEPR theory depends not just on what atoms are bonded, but on all regions of electron density around the central atom—including lone pairs. Carbon and sulfur have different numbers of valence electrons and different abilities to expand their octets, so they end up with different electron geometries. Once you know how many lone pairs surround each central atom, you can predict whether the molecule bends or stays linear, and that geometry directly determines whether the bond dipoles cancel out or add up to create a net molecular dipole.