Which of the following arrangements shows the correct order of decreasing paramagnetism?

Options

A. NgtAlgtOgtCa
B. NgtOgtAlgtCa
C. OgtNgtAlgtCa
D. OgtNgtCagtAl

Answer

To determine the correct order of decreasing paramagnetism among the given elements (Nitrogen, Oxygen, Aluminum, and Calcium), we need to analyze their electronic configurations and count the number of unpaired electrons. The more unpaired electrons an atom has, the more paramagnetic it is.

### Step-by-Step Solution:

1. **Identify the Elements and Their Atomic Numbers:**
- Nitrogen (N) - Atomic number 7
- Oxygen (O) - Atomic number 8
- Aluminum (Al) - Atomic number 13
- Calcium (Ca) - Atomic number 20

2. **Write the Electronic Configurations:**
- **Nitrogen (N)**:
- Atomic number 7 → Electronic configuration: 1s² 2s² 2p³
- **Oxygen (O)**:
- Atomic number 8 → Electronic configuration: 1s² 2s² 2p⁴
- **Aluminum (Al)**:
- Atomic number 13 → Electronic configuration: 1s² 2s² 2p⁶ 3s² 3p¹
- **Calcium (Ca)**:
- Atomic number 20 → Electronic configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

3. **Count the Number of Unpaired Electrons:**
- **Nitrogen (N)**:
- 2p³ has 3 unpaired electrons (↑ ↑ ↑)
- **Oxygen (O)**:
- 2p⁴ has 2 unpaired electrons (↑ ↑ ↑↓)
- **Aluminum (Al)**:
- 3p¹ has 1 unpaired electron (↑)
- **Calcium (Ca)**:
- 4s² has 0 unpaired electrons (paired)

4. **Arrange the Elements Based on the Number of Unpaired Electrons:**
- Nitrogen (N): 3 unpaired electrons
- Oxygen (O): 2 unpaired electrons
- Aluminum (Al): 1 unpaired electron
- Calcium (Ca): 0 unpaired electrons

5. **Order of Decreasing Paramagnetism:**
- The order of decreasing paramagnetism based on the number of unpaired electrons is:
- Nitrogen (N) > Oxygen (O) > Aluminum (Al) > Calcium (Ca)

### Final Answer:
The correct order of decreasing paramagnetism is:
**N > O > Al > Ca**