How many of these molecules are diamagnetic and have bond order more than 2
`O_(2)^(2+), CO, overset(-)CN, NO, NO^(+), N_(2), O_(2)^(+), N_(2)^(2-), O_(2)^(2-)`

Answer

To determine how many of the given molecules are diamagnetic and have a bond order greater than 2, we will follow these steps:

### Step 1: Identify the total number of electrons for each molecule
We will calculate the total number of electrons for each molecule based on their atomic numbers.

1. **O₂²⁺**: Oxygen (O) has an atomic number of 8. For O₂, total electrons = 2 × 8 = 16. For O₂²⁺, we subtract 2 electrons: 16 - 2 = 14.
2. **CO**: Carbon (C) has an atomic number of 6, and Oxygen (O) has an atomic number of 8. Total electrons = 6 + 8 = 14.
3. **CN⁻**: Carbon (C) = 6, Nitrogen (N) = 7. Total = 6 + 7 + 1 (for the negative charge) = 14.
4. **NO**: Nitric oxide has 7 (N) + 8 (O) = 15 electrons.
5. **NO⁺**: Total = 7 + 8 - 1 (for the positive charge) = 14.
6. **N₂**: Nitrogen has an atomic number of 7. Total = 2 × 7 = 14.
7. **O₂⁺**: Total = 16 - 1 (for the positive charge) = 15.
8. **N₂²⁻**: Total = 14 + 2 (for the negative charge) = 16.
9. **O₂²⁻**: Total = 16 + 2 = 18.

### Step 2: Determine the bond order for each molecule
Using the bond order calculation method mentioned in the transcript:

- **O₂²⁺**: 14 electrons → Bond order = 3.
- **CO**: 14 electrons → Bond order = 3.
- **CN⁻**: 14 electrons → Bond order = 2.5.
- **NO**: 15 electrons → Bond order = 2.5.
- **NO⁺**: 14 electrons → Bond order = 3.
- **N₂**: 14 electrons → Bond order = 3.
- **O₂⁺**: 15 electrons → Bond order = 2.5.
- **N₂²⁻**: 16 electrons → Bond order = 2.
- **O₂²⁻**: 18 electrons → Bond order = 1.

### Step 3: Determine if the molecules are diamagnetic or paramagnetic
A molecule is diamagnetic if it has all paired electrons (even total number of electrons) and paramagnetic if it has unpaired electrons (odd total number of electrons).

1. **O₂²⁺**: 14 electrons (even) → Diamagnetic.
2. **CO**: 14 electrons (even) → Diamagnetic.
3. **CN⁻**: 14 electrons (even) → Diamagnetic.
4. **NO**: 15 electrons (odd) → Paramagnetic.
5. **NO⁺**: 14 electrons (even) → Diamagnetic.
6. **N₂**: 14 electrons (even) → Diamagnetic.
7. **O₂⁺**: 15 electrons (odd) → Paramagnetic.
8. **N₂²⁻**: 16 electrons (even) → Diamagnetic.
9. **O₂²⁻**: 18 electrons (even) → Diamagnetic.

### Step 4: Compile the results
Now we will summarize which of these molecules are diamagnetic and have a bond order greater than 2:

- **O₂²⁺**: Diamagnetic, Bond order = 3.
- **CO**: Diamagnetic, Bond order = 3.
- **CN⁻**: Diamagnetic, Bond order = 2.5 (not greater than 2).
- **NO**: Paramagnetic.
- **NO⁺**: Diamagnetic, Bond order = 3.
- **N₂**: Diamagnetic, Bond order = 3.
- **O₂⁺**: Paramagnetic.
- **N₂²⁻**: Diamagnetic, Bond order = 2 (not greater than 2).
- **O₂²⁻**: Diamagnetic, Bond order = 1 (not greater than 2).

### Conclusion
The molecules that are diamagnetic and have a bond order greater than 2 are:
1. O₂²⁺
2. CO
3. NO⁺
4. N₂

Thus, the total number of molecules that are diamagnetic and have a bond order greater than 2 is **4**.

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