The ratio of `sigma-` bond and `pi-` bond in tetracryano ethylene is `:`

Options

A. `2 :1`
B. `1 :1`
C. `1 : 2`
D. none of these

Explanation

To find the ratio of sigma (σ) bonds to pi (π) bonds in tetracyanoethylene (C6N4), we will follow these steps:

### Step 1: Understand the Structure of Tetracyanoethylene
Tetracyanoethylene consists of a central ethylene (C=C) unit with four cyano (C≡N) groups attached to it. The molecular formula is C6N4.

### Step 2: Draw the Lewis Structure
The structure can be visualized as follows:
- Two carbon atoms are double-bonded to each other (C=C).
- Each carbon atom is also bonded to a cyano group (C≡N).

### Step 3: Count the Sigma Bonds
1. **Between the two carbon atoms (C=C)**: There is 1 sigma bond.
2. **Between each carbon atom and the cyano groups**: Each C≡N bond contains 1 sigma bond. Since there are 4 cyano groups, this contributes 4 sigma bonds.
3. **Total sigma bonds**:
- 1 (C=C) + 4 (C≡N) = 5 sigma bonds.

### Step 4: Count the Pi Bonds
1. **Between the two carbon atoms (C=C)**: There is 1 pi bond.
2. **Between each carbon atom and the cyano groups**: Each C≡N bond contains 2 pi bonds. Since there are 4 cyano groups, this contributes 8 pi bonds.
3. **Total pi bonds**:
- 1 (from C=C) + 8 (from C≡N) = 9 pi bonds.

### Step 5: Calculate the Ratio of Sigma to Pi Bonds
Now that we have the total counts:
- Total sigma bonds = 5
- Total pi bonds = 9

The ratio of sigma to pi bonds is:
\[ \text{Ratio} = \frac{\text{Total Sigma Bonds}}{\text{Total Pi Bonds}} = \frac{5}{9} \]

### Final Answer
The ratio of sigma bonds to pi bonds in tetracyanoethylene is **5:9**.

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