In Which of the following the double bond consist of the pi bonds .

Options

A. `O_(2)`
B. `Be_(2)`
C. `C_(2)`
D. `S_(2)`

Explanation

To determine which of the following molecules has a double bond consisting solely of pi bonds, we need to analyze the bonding in each molecule. Let's break down the problem step by step.

### Step 1: Understand the nature of double bonds
A double bond between two atoms consists of one sigma (σ) bond and one pi (π) bond. However, the question asks for a double bond that consists only of pi bonds. This means we are looking for a scenario where there is no sigma bond present.

### Step 2: Analyze the options
We will analyze the bonding in the given molecules: O2, Be2, and C2.

#### Option 1: O2 (Oxygen)
- Oxygen has the electron configuration: 1s² 2s² 2p⁴.
- In O2, the two oxygen atoms will overlap their p orbitals to form bonds.
- The molecular orbital (MO) theory shows that O2 has one sigma bond (σ) and one pi bond (π).
- Therefore, O2 does not meet the requirement as it contains a sigma bond.

#### Option 2: Be2 (Beryllium)
- Beryllium has the electron configuration: 1s² 2s².
- In Be2, there are no available p orbitals for pi bonding since beryllium only has s orbitals in its valence shell.
- Thus, Be2 cannot form a double bond consisting of pi bonds, as it does not have any pi bonds at all.

#### Option 3: C2 (Carbon)
- Carbon has the electron configuration: 1s² 2s² 2p².
- In C2, the two carbon atoms can overlap their p orbitals to form bonds.
- According to molecular orbital theory, C2 has two pi bonds formed from the 2p orbitals and one sigma bond.
- However, since we are looking for a double bond consisting solely of pi bonds, we need to check the filling of the orbitals.
- C2 has a total of 4 electrons in the 2p orbitals, which can fill the two pi orbitals (π2px and π2py) without any electrons in the sigma orbital (σ2pz).
- This means that C2 can indeed have a double bond that consists only of pi bonds.

### Conclusion
After analyzing all the options, we conclude that the molecule with a double bond consisting solely of pi bonds is **C2**.