Carbon suboxide `(C_3 O_2)` has recently be shown as a component of the atmosphere of venus. Which of the following formulations represent the correct ground state Lewis structure for carbon suboxide?

Options

A.
B.
C.
D.

Answer

To determine the correct ground state Lewis structure for carbon suboxide `(C₃O₂)`, we can follow these steps:

### Step 1: Calculate the Total Number of Valence Electrons
- Each carbon atom has 4 valence electrons, and there are 3 carbon atoms.
- Each oxygen atom has 6 valence electrons, and there are 2 oxygen atoms.
- Total valence electrons = (3 × 4) + (2 × 6) = 12 + 12 = 24 valence electrons.

### Step 2: Draw a Skeleton Structure
- Place the carbon atoms in the center and the oxygen atoms at the terminal positions since oxygen is more electronegative.
- A possible skeleton structure can be represented as: `O - C - C - C - O`.

### Step 3: Distribute Electrons to Satisfy the Octet Rule
- Start by placing a single bond (1 pair of electrons) between each atom in the skeleton structure.
- After placing the bonds, we will have used 6 electrons (3 bonds).
- Remaining electrons = 24 - 6 = 18 electrons.

### Step 4: Complete the Octets of the Terminal Atoms (Oxygen)
- Each oxygen needs 6 more electrons to complete its octet.
- Place 3 lone pairs (6 electrons) on each oxygen atom.
- Now, we have used 6 (for the bonds) + 12 (for the lone pairs on oxygen) = 18 electrons.
- Remaining electrons = 24 - 18 = 6 electrons.

### Step 5: Distribute Remaining Electrons to Carbon Atoms
- Distribute the remaining 6 electrons to the carbon atoms.
- Place 1 lone pair (2 electrons) on the central carbon atom.
- Now, we have used 20 electrons (6 + 12 + 2 = 20).
- Remaining electrons = 24 - 20 = 4 electrons.

### Step 6: Adjust Bonds to Satisfy the Octet Rule
- The central carbon atom currently has only 6 electrons around it (2 from the lone pair and 4 from the bonds).
- To satisfy the octet rule, we can shift one lone pair from each oxygen to form double bonds with the central carbon.
- This results in the structure: `O=C=C=C=O`.

### Step 7: Check Formal Charges
- Calculate the formal charges to ensure the stability of the structure.
- For each oxygen:
- Lone pairs = 4, shared pairs = 2 (1 bond with carbon), so formal charge = 6 - (4 + 1) = 1.
- For the central carbon:
- Lone pairs = 0, shared pairs = 4 (2 bonds with each oxygen), so formal charge = 4 - 4 = 0.
- For the terminal carbon:
- Lone pairs = 0, shared pairs = 4 (2 bonds with the central carbon), so formal charge = 4 - 4 = 0.

### Step 8: Finalize the Structure
- The final Lewis structure for carbon suboxide `(C₃O₂)` is:
```
O=C=C=C=O
```
- All atoms have complete octets, and the formal charges are minimized.