CS2 Lewis Structure: what must be shown
The cs2 lewis structure (carbon disulfide) must account for all valence electrons, satisfy the octet rule for carbon and sulfur, and minimize formal charges. The most stable Lewis structure places carbon in the center and uses multiple bonding to complete carbon’s octet.
Step 1: Count total valence electrons
Carbon contributes 4 valence electrons, and each sulfur contributes 6:
\[ N_{\text{valence}} = 4 + 2(6) = 16 \]
Electron bookkeeping goal: place a total of 16 valence electrons as bonding pairs and lone pairs in the CS2 Lewis structure.
Step 2: Choose the skeletal structure
Carbon is the least electronegative atom among C and S and is therefore placed as the central atom. The skeleton is: \[ \text{S–C–S} \]
Two single bonds use \(2 \times 2 = 4\) electrons, leaving \(16 - 4 = 12\) electrons to distribute as lone pairs.
Step 3: Complete octets and determine bond order
If the remaining 12 electrons are placed as lone pairs on the sulfurs, each sulfur reaches an octet, but carbon would have only 4 electrons (two single bonds), which violates the octet rule for carbon.
To give carbon an octet, lone-pair electrons from each sulfur are converted into bonding pairs with carbon, forming two double bonds: \[ \text{S}=\text{C}=\text{S} \]
This structure gives carbon 8 electrons in bonds (two double bonds) and leaves each sulfur with two lone pairs.
Step 4: Verify formal charges
Formal charge is computed using: \[ \text{FC} = V - N - \frac{B}{2} \] where \(V\) is valence electrons for the free atom, \(N\) is nonbonding electrons, and \(B\) is bonding electrons around the atom in the Lewis structure.
| Atom | \(V\) | \(N\) (nonbonding e⁻) | \(B\) (bonding e⁻) | \(\text{FC} = V - N - \dfrac{B}{2}\) |
|---|---|---|---|---|
| C (central) | 4 | 0 | 8 | \(4 - 0 - \dfrac{8}{2} = 0\) |
| S (left) | 6 | 4 | 4 | \(6 - 4 - \dfrac{4}{2} = 0\) |
| S (right) | 6 | 4 | 4 | \(6 - 4 - \dfrac{4}{2} = 0\) |
Conclusion: The CS2 Lewis structure with two C=S double bonds gives zero formal charge on all atoms, which is the preferred representation.
Visualization: CS2 Lewis structure (lone pairs and double bonds)
Geometry and hybridization implied by the Lewis structure
Carbon has two electron domains (two double bonds count as two regions of electron density), so VSEPR predicts a linear molecular geometry with an approximate bond angle of \(180^\circ\). The central carbon is commonly described as sp hybridized in this linear arrangement.