Which is a correct Lewis Structure for CS2? A. S=C=S B. C-S=S C. C=S=S D. C≡C E. S=C=S
The Correct Answer and Explanation is:
The correct Lewis structure for carbon disulfide (CS₂) is:
A. S=C=S
Explanation:
Carbon disulfide (CS₂) is a linear molecule composed of one carbon atom and two sulfur atoms. To determine the correct Lewis structure, we follow a systematic approach:
1. Count Total Valence Electrons:
- Carbon (C) has 4 valence electrons.
- Each sulfur (S) has 6 valence electrons.
- Total: 4 + 6×2 = 16 valence electrons
2. Determine the Central Atom:
Carbon is less electronegative than sulfur, so carbon becomes the central atom, flanked by the two sulfur atoms.
3. Form Initial Bonds:
Draw single bonds between the carbon and each sulfur:
- S–C–S
This uses 2 bonds = 4 electrons, leaving 12 electrons to distribute.
4. Complete Octets:
Place 6 electrons (three lone pairs) on each sulfur atom:
- This uses up all 12 remaining electrons.
However, this structure gives carbon only 4 electrons, which is not enough to complete its octet. To fix this, create double bonds between carbon and each sulfur:
S=C=S
This structure:
- Has 4 electrons (two bonds) between C and each S
- Gives carbon 8 electrons (full octet)
- Gives each sulfur 8 electrons (2 bonding + 2 lone pairs)
5. Check Formal Charges:
- Carbon: 4 valence − 0 lone pairs − 4 bonds = 0
- Sulfur: 6 valence − 4 lone electrons − 2 bonds = 0
All atoms have formal charges of zero, indicating a stable structure.
6. Geometry:
The molecule is linear, with bond angles of 180°, due to the arrangement of electron domains around the central carbon.
Final Answer:
A. S=C=S is the correct Lewis structure for CS₂.
