How many unpaired electrons are present in `NO` molecule ?

Answer

To determine the number of unpaired electrons in the nitrogen monoxide (NO) molecule, we can follow these steps:

### Step 1: Determine the electronic configuration of nitrogen and oxygen
- Nitrogen (N) has an atomic number of 7, so its electronic configuration is:
\[ 1s^2 \, 2s^2 \, 2p^3 \]
- Oxygen (O) has an atomic number of 8, so its electronic configuration is:
\[ 1s^2 \, 2s^2 \, 2p^4 \]

### Step 2: Combine the electrons from nitrogen and oxygen
- The total number of valence electrons in the NO molecule is:
\[ \text{Total electrons} = \text{Electrons from N} + \text{Electrons from O} = 5 + 6 = 11 \]

### Step 3: Construct the molecular orbital diagram
- In the molecular orbital theory, the 11 electrons will fill the molecular orbitals in the following order:
- \( \sigma_{1s}^2 \)
- \( \sigma_{1s}^2 \)
- \( \sigma_{2s}^2 \)
- \( \sigma_{2s}^2 \)
- \( \sigma_{2p_z}^2 \) (bonding orbital)
- \( \pi_{2p_x}^2 \) (bonding orbital)
- \( \pi_{2p_y}^2 \) (bonding orbital)
- \( \pi^*_{2p_x}^1 \) (antibonding orbital)

### Step 4: Count the unpaired electrons
- From the filling of the molecular orbitals, we see that:
- The \( \pi^*_{2p_x} \) orbital has 1 electron, which is unpaired.
- Therefore, the total number of unpaired electrons in the NO molecule is:
\[ \text{Number of unpaired electrons} = 1 \]

### Conclusion
The NO molecule has **1 unpaired electron**.

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