The common features among the species `CN^-, CO` and `NO^+`

Options

A. Bond order three and isoelectronic
B. Bond order three and weak field ligands
C. Bond order two and `pi`- acceptors
D. Isoelectronic and weak field ligands

Answer

To find the common features among the species CN^-, CO, and NO^+, we will follow these steps:

### Step 1: Determine the Total Number of Electrons
1. **For CO (Carbon Monoxide)**:
- Carbon (C) has 6 electrons.
- Oxygen (O) has 8 electrons.
- Total = 6 + 8 = 14 electrons.

2. **For CN^- (Cyanide Ion)**:
- Carbon (C) has 6 electrons.
- Nitrogen (N) has 7 electrons.
- The negative charge adds 1 electron.
- Total = 6 + 7 + 1 = 14 electrons.

3. **For NO^+ (Nitric Oxide Cation)**:
- Nitrogen (N) has 7 electrons.
- Oxygen (O) has 8 electrons.
- The positive charge subtracts 1 electron.
- Total = 7 + 8 - 1 = 14 electrons.

### Step 2: Identify Isoelectronic Species
All three species (CO, CN^-, and NO^+) have the same total number of electrons, which is 14. Therefore, they are isoelectronic, meaning they have the same number of electrons and similar electronic structures.

### Step 3: Determine Molecular Orbital Configuration
1. **For CO**:
- The molecular orbital configuration is:
- σ1s² σ*1s² σ2s² σ*2s² (2 electrons each)
- π2p_x² π2p_y² (2 electrons each)
- σ2p_z² (2 electrons)
- Total = 14 electrons.

2. **For CN^-**:
- The molecular orbital configuration is the same as CO:
- σ1s² σ*1s² σ2s² σ*2s² (2 electrons each)
- π2p_x² π2p_y² (2 electrons each)
- σ2p_z² (2 electrons)
- Total = 14 electrons.

3. **For NO^+**:
- The molecular orbital configuration is also the same:
- σ1s² σ*1s² σ2s² σ*2s² (2 electrons each)
- π2p_x² π2p_y² (2 electrons each)
- σ2p_z² (2 electrons)
- Total = 14 electrons.

### Step 4: Calculate Bond Order
The bond order can be calculated using the formula:
\[ \text{Bond Order} = \frac{1}{2} \times (\text{Number of electrons in bonding orbitals} - \text{Number of electrons in antibonding orbitals}) \]

1. **For CO**:
- Bonding orbitals: 10 electrons (σ1s, σ2s, π2p_x, π2p_y, σ2p_z)
- Antibonding orbitals: 4 electrons (σ*1s, σ*2s)
- Bond Order = 1/2 * (10 - 4) = 3.

2. **For CN^-**:
- Same calculation as CO gives a bond order of 3.

3. **For NO^+**:
- Same calculation as CO gives a bond order of 3.

### Conclusion
The common features among CN^-, CO, and NO^+ are:
- They are isoelectronic (all have 14 electrons).
- They have the same bond order of 3.