Draw the Lewis dot structure and two resonance forms for the monothiocarbonate ion: CO2S2 When drawing your structures, be certain to include lone pair electrons and formal charges.
1. Draw the best Lewis dot structure for the anion CCl3 in the correct molecular geometry [Include formal charges and lone pair electrons, and use dashed and solid wedge bonds if necessary]
2. How many electron groups are present around the central atom and what is the electron group geometry?
3. What is the molecular geometry and ideal bond angles?
4. Is the molecule polar or nonpolar? If it is polar, draw a dipole moment arrow next to your structure to indicate the directionality of the dipole moment,
The Correct Answer and Explanation is :
Lewis Dot Structure for the Monothiocarbonate Ion (CO2S2):
The molecular formula for the monothiocarbonate ion is CO₂S₂. To draw the Lewis dot structure, we need to consider the bonding and lone pairs of electrons.
- Carbon (C) is the central atom and will form bonds with both oxygen (O) and sulfur (S).
- Oxygen atoms are highly electronegative and will likely form double bonds with carbon, while sulfur (which is less electronegative) will form a single bond with carbon.
Here’s how you draw the Lewis dot structure for CO₂S₂:
- Carbon (C) will be in the center, and it will form double bonds with two oxygen atoms, one single bond with sulfur.
- The sulfur atom will have lone pairs of electrons and will carry a formal negative charge.
- The oxygen atoms will also have lone pairs of electrons and formal charges.
- The overall charge is -1, so the formal charges will be distributed in a way that the structure minimizes energy.
Here’s the best structure (with formal charges):
- C double bonded to O (with 2 lone pairs on oxygen), and C single bonded to S (with 2 lone pairs on sulfur).
- Each oxygen atom will carry a formal negative charge, and the sulfur atom may carry a formal negative charge.
Resonance Forms:
- Resonance occurs when there are multiple possible structures with the same skeletal formula but differing electron distributions. In the case of the monothiocarbonate ion, the sulfur and oxygen atoms can swap roles in terms of bonding with carbon, leading to different resonance forms.
For the CCl₃ molecule:
1. Lewis Dot Structure for CCl₃:
- Carbon (C) is the central atom.
- Three chlorine (Cl) atoms are single-bonded to the carbon atom.
- Lone pairs are present on each chlorine atom.
The formal charges are zero on the central carbon atom, while each chlorine atom has three lone pairs and is connected to the carbon atom by a single bond. Each chlorine atom has a formal charge of zero because it shares one electron with carbon.
2. Electron Groups around the Central Atom:
- The central carbon has three bonding pairs of electrons (from the three Cl atoms) and no lone pairs.
- This gives us three electron groups around the central atom.
3. Electron Group Geometry:
- With three electron groups, the electron geometry is trigonal planar.
4. Molecular Geometry and Bond Angles:
- Since there are no lone pairs on the central atom and the three bonds are identical, the molecular geometry is also trigonal planar.
- The ideal bond angles in a trigonal planar geometry are 120°.
5. Polarity:
- CCl₃ is polar. Although the C-Cl bonds are polar (due to the electronegativity difference between C and Cl), the symmetry of the molecule does not cancel the dipoles. The molecule’s asymmetry leads to a net dipole moment pointing towards the chlorine atoms.
To indicate polarity, a dipole moment arrow would point from the central carbon atom to the chlorine atoms.
Conclusion:
- The Lewis structure for the monothiocarbonate ion (CO₂S₂) shows resonance between different bonding configurations.
- For CCl₃, the trigonal planar geometry and polarity arise from the uneven distribution of electron density due to the electronegativity difference.