Which of the following molecule has highest bond energy ?

Options

A. F-F
B. N-N
C. C-C
D. O-O

Explanation

To determine which of the given molecules has the highest bond energy, we will analyze the bond order and the presence of lone pairs in each molecule. The molecules provided are:

1. Fluorine (F2)
2. Nitrogen (N2)
3. Carbon (C2)
4. Oxygen (O2)

### Step-by-Step Solution:

**Step 1: Identify the bond order of each molecule.**
- **F2 (Fluorine)**: The bond order is 1 (single bond).
- **N2 (Nitrogen)**: The bond order is 3 (triple bond).
- **C2 (Carbon)**: The bond order is 1 (single bond).
- **O2 (Oxygen)**: The bond order is 2 (double bond).

**Step 2: Consider the presence of lone pairs.**
- **F2**: Each fluorine atom has 3 lone pairs, leading to lone pair-lone pair repulsion.
- **N2**: Each nitrogen atom has 1 lone pair, which is less than fluorine.
- **C2**: No lone pairs are present, thus no lone pair-lone pair repulsion.
- **O2**: Each oxygen atom has 2 lone pairs, which can cause some repulsion.

**Step 3: Analyze the effect of lone pairs on bond energy.**
- Lone pair-lone pair repulsion increases the bond length and decreases the bond energy.
- In F2, the presence of three lone pairs on each atom leads to significant repulsion, resulting in lower bond energy.
- In N2, the presence of one lone pair on each nitrogen atom also contributes to some repulsion but is less than in F2.
- In O2, the presence of two lone pairs on each oxygen atom leads to moderate repulsion.
- In C2, the absence of lone pairs means there is no repulsion, allowing for a stronger bond.

**Step 4: Compare the bond energies.**
- F2 has the lowest bond energy due to high lone pair repulsion.
- N2 has a higher bond energy than F2 but lower than C2.
- O2 has a bond energy that is lower than N2 due to the presence of lone pairs.
- C2 has the highest bond energy because it has no lone pairs and a single bond.

**Conclusion:**
The molecule with the highest bond energy among the given options is **C2 (Carbon)**.