The explanation for the presence of three unpaired electrons in the nitrogen atom can be given by -

Options

A. Pauli's exclusion principle
B. Hund's rule
C. Aufbau's principle
D. Uncertainity principle

Answer

To explain the presence of three unpaired electrons in the nitrogen atom, we can follow these steps:

### Step 1: Understand the Electron Configuration of Nitrogen
- The atomic number of nitrogen (N) is 7, which means it has 7 electrons.
- The electron configuration of nitrogen is 1s² 2s² 2p³.

### Step 2: Identify the Valence Shell
- The outermost shell for nitrogen is the second shell (n=2), which contains the 2s and 2p orbitals.
- In this shell, the 2s orbital is fully filled with 2 electrons, and the 2p orbital has 3 electrons.

### Step 3: Apply Hund's Rule
- Hund's rule states that electrons will occupy degenerate orbitals (orbitals of the same energy) singly before pairing up.
- The 2p subshell consists of three orbitals: 2p_x, 2p_y, and 2p_z.

### Step 4: Filling the 2p Orbitals
- According to Hund's rule, the three electrons in the 2p subshell will fill each of the three 2p orbitals singly before any pairing occurs.
- Therefore, the configuration in the 2p subshell will be:
- 2p_x: ↑
- 2p_y: ↑
- 2p_z: ↑
- This results in three unpaired electrons.

### Conclusion
- Thus, the presence of three unpaired electrons in the nitrogen atom can be explained by Hund's rule, which dictates that electrons fill degenerate orbitals singly before pairing up.

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