How many electrons are unpaired in
(i) He ? (ii) C?
(iii) N? (iv) K?

Answer

To determine the number of unpaired electrons in the elements Helium (He), Carbon (C), Nitrogen (N), and Potassium (K), we will follow these steps:

### Step 1: Determine the Atomic Number
- **He**: Atomic number = 2
- **C**: Atomic number = 6
- **N**: Atomic number = 7
- **K**: Atomic number = 19

### Step 2: Write the Electronic Configuration
1. **Helium (He)**:
- Electronic configuration: 1s²
- Orbital configuration: 1s²
- Unpaired electrons: 0 (since both electrons are paired)

2. **Carbon (C)**:
- Electronic configuration: 1s² 2s² 2p²
- Orbital configuration:
- 1s: ↑↓ (2 electrons)
- 2s: ↑↓ (2 electrons)
- 2p: ↑ ↑ (2 electrons in separate orbitals, according to Hund's rule)
- Unpaired electrons: 2 (the two 2p electrons are unpaired)

3. **Nitrogen (N)**:
- Electronic configuration: 1s² 2s² 2p³
- Orbital configuration:
- 1s: ↑↓ (2 electrons)
- 2s: ↑↓ (2 electrons)
- 2p: ↑ ↑ ↑ (3 electrons, one in each orbital)
- Unpaired electrons: 3 (all three 2p electrons are unpaired)

4. **Potassium (K)**:
- Electronic configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
- Orbital configuration:
- 1s: ↑↓ (2 electrons)
- 2s: ↑↓ (2 electrons)
- 2p: ↑↑↑ (6 electrons)
- 3s: ↑↓ (2 electrons)
- 3p: ↑↑↑ (6 electrons)
- 4s: ↑ (1 electron)
- Unpaired electrons: 1 (the single 4s electron is unpaired)

### Summary of Unpaired Electrons:
- **He**: 0 unpaired electrons
- **C**: 2 unpaired electrons
- **N**: 3 unpaired electrons
- **K**: 1 unpaired electron