The bond order of which of the following molecules/ ion(s) is 3

Options

A. `O_2 and NO^(+)`
B. `N_2 and NO^(+)`
C. `N_2 and NO`
D. `N_2^(+) and NO^(+)`

Explanation

To determine the bond order of the given molecules or ions and identify which has a bond order of 3, we can follow these steps:

### Step 1: Understand Bond Order
Bond order is defined as the number of bonds between two atoms. It can be calculated using the formula:
\[ \text{Bond Order} = \frac{(N_b - N_a)}{2} \]
where \( N_b \) is the number of bonding electrons and \( N_a \) is the number of antibonding electrons.

### Step 2: Identify the Molecules/Ions
We need to analyze the following species:
1. O2
2. NO+
3. N2
4. N2+

### Step 3: Calculate the Total Electrons for Each Species
- **O2**: Oxygen has 8 electrons, so O2 has \( 8 + 8 = 16 \) electrons.
- **NO+**: Nitrogen has 7 electrons and Oxygen has 8. Therefore, NO+ has \( 7 + 8 - 1 = 14 \) electrons (subtracting one for the positive charge).
- **N2**: Each nitrogen has 7 electrons, so N2 has \( 7 + 7 = 14 \) electrons.
- **N2+**: N2 has 14 electrons, and removing one for the positive charge gives \( 14 - 1 = 13 \) electrons.

### Step 4: Determine Isoelectronic Species
Species that have the same number of electrons are called isoelectronic. In this case:
- O2 (16 electrons)
- NO+ (14 electrons)
- N2 (14 electrons)
- N2+ (13 electrons)

### Step 5: Calculate Bond Order for Each Species
- **For N2**:
- Bonding electrons = 10, Antibonding electrons = 0
- Bond Order = \( \frac{(10 - 0)}{2} = 5 \)

- **For NO+**:
- Bonding electrons = 10, Antibonding electrons = 1
- Bond Order = \( \frac{(10 - 1)}{2} = 4.5 \)

- **For O2**:
- Bonding electrons = 10, Antibonding electrons = 6
- Bond Order = \( \frac{(10 - 6)}{2} = 2 \)

- **For N2+**:
- Bonding electrons = 9, Antibonding electrons = 1
- Bond Order = \( \frac{(9 - 1)}{2} = 4 \)

### Step 6: Identify the Species with Bond Order of 3
From the calculations:
- N2 has a bond order of 3.
- NO+ has a bond order of 4.5.
- O2 has a bond order of 2.
- N2+ has a bond order of 4.

Thus, the only species with a bond order of 3 is **N2**.

### Final Answer
The bond order of **N2** is 3.

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