Among the following which one is not paramagnetic ? [ Atomic numbers , `Be =4, Ne =10`,As =33 ,Cl=17]`

Options

A. `Ne^(2+)`
B. `Be^(+)`
C. `Cl^(-)`
D. `As^(+)`

Answer

To determine which of the given elements is not paramagnetic, we need to analyze the electronic configurations of each element and check for the presence of unpaired electrons. A substance is considered paramagnetic if it has at least one unpaired electron.

### Step-by-Step Solution:

1. **Identify the Elements and Their Atomic Numbers:**
- Be (Beryllium) - Atomic Number: 4
- Ne (Neon) - Atomic Number: 10
- Cl (Chlorine) - Atomic Number: 17
- As (Arsenic) - Atomic Number: 33

2. **Determine the Electronic Configuration of Each Element:**
- **Beryllium (Be):**
- Atomic Number: 4
- Electronic Configuration: 1s² 2s²
- For Be⁺ (removing one electron): 1s² 2s¹ (1 unpaired electron)

- **Neon (Ne):**
- Atomic Number: 10
- Electronic Configuration: 1s² 2s² 2p⁶
- For Ne²⁺ (removing two electrons): 1s² 2s² 2p⁴ (4 electrons in p orbitals)
- The p orbitals will have 2 unpaired electrons (paramagnetic).

- **Chlorine (Cl):**
- Atomic Number: 17
- Electronic Configuration: 1s² 2s² 2p⁶ 3s² 3p⁵
- For Cl⁻ (adding one electron): 1s² 2s² 2p⁶ 3s² 3p⁶ (all electrons paired)
- Therefore, Cl⁻ is diamagnetic (not paramagnetic).

- **Arsenic (As):**
- Atomic Number: 33
- Electronic Configuration: [Ar] 3d¹⁰ 4s² 4p³
- For As³⁺ (removing three electrons): [Ar] 3d¹⁰ 4s² 4p¹ (1 unpaired electron)

3. **Conclusion:**
- Among the given elements, **Chlorine (Cl)** in its anionic form (Cl⁻) has all paired electrons and is therefore **not paramagnetic**.

### Final Answer:
The element that is **not paramagnetic** is **Chlorine (Cl)**.

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