Which of the following is the most likely Lewis structure for CS2 and why? Use your determinations in Parts 1-3 to help you decide: Choose one: A. C-S-S; the atom that can form the most bonds is in the center B. S-C-S; the atom that can form the most bonds is in the center C. C-S-S; formal charges are minimized D. S-C-S; formal charges are minimized
The Correct Answer and Explanation is:
The correct answer is: D. S=C=S; formal charges are minimized
Explanation:
To determine the most likely Lewis structure for carbon disulfide (CS₂), we must consider several key principles: octet rule, formal charge minimization, and bonding capacities of atoms.
1. Choosing the Central Atom
Carbon (C) is more likely to be the central atom because it can form four covalent bonds, whereas sulfur (S) typically forms only two. Central atoms are usually the ones that can form the most bonds and are less electronegative, which is true for carbon compared to sulfur.
2. Total Valence Electrons
- Carbon has 4 valence electrons.
- Each sulfur has 6 valence electrons.
- Total = 4 (C) + 6×2 (S) = 16 valence electrons
3. Drawing the Skeleton Structure
Placing carbon in the center: S–C–S
This linear structure allows for bonding on both sides. Next, we add bonding and lone pairs.
4. Satisfying the Octet Rule and Minimizing Formal Charges
To satisfy the octet rule:
- Carbon needs 8 electrons → needs 4 bonds.
- Sulfur also wants 8 electrons → typically forms 2 bonds.
A structure with double bonds between carbon and each sulfur (S=C=S) allows all atoms to achieve full octets:
- Carbon forms 4 bonds (2 with each sulfur).
- Each sulfur has two bonding pairs and two lone pairs.
This arrangement minimizes formal charges:
- Formal charge on each atom is zero, which is ideal and indicates a stable structure.
Alternate structures like C–S–S or C–S single bonds would result in formal charges that are not minimized or would violate the octet rule for carbon.
Conclusion
The most likely Lewis structure for CS₂ is D. S=C=S, with double bonds on both sides of carbon. This structure obeys the octet rule and minimizes formal charges, making it the most stable and chemically accurate representation.
