Which of the following species in paramagnetic:

Options

A. `CN^(-)`
B. `SnCl_(2)`
C. `C_(2)H_(2)`
D. `NO_(2)`

Answer

To determine which of the following species is paramagnetic, we need to identify the presence of unpaired electrons in their electronic configurations. Paramagnetic species have one or more unpaired electrons, while diamagnetic species have all electrons paired.

### Step-by-Step Solution:

1. **Identify the Species**: We need to analyze the electronic configurations of the given species to check for unpaired electrons. The species we will consider are:
- Cyanide (CN⁻)
- Tin(IV) chloride (SnCl₄)
- Acetylene (C₂H₂)
- Nitrogen dioxide (NO₂)

2. **Cyanide (CN⁻)**:
- Carbon (C) has 6 electrons, and Nitrogen (N) has 7 electrons.
- The cyanide ion (CN⁻) has an additional electron due to the negative charge.
- Total electrons = 6 (C) + 7 (N) + 1 (extra electron) = 14 electrons.
- Since 14 is even, all electrons are paired. Thus, CN⁻ is **diamagnetic**.

3. **Tin(IV) chloride (SnCl₄)**:
- Tin (Sn) belongs to the carbon family and has 50 electrons (electronic configuration: [Kr] 5s² 4d¹⁰).
- In SnCl₄, Sn loses 4 electrons (2 from 5s and 2 from 4d), leaving it with 4 paired electrons.
- Therefore, SnCl₄ has no unpaired electrons and is **diamagnetic**.

4. **Acetylene (C₂H₂)**:
- Each carbon atom has 6 electrons, and there are 2 carbon atoms in C₂H₂.
- Total electrons = 2 × 6 (C) + 2 (H) = 14 electrons.
- The structure of C₂H₂ shows that all electrons are paired in the bonding, resulting in no unpaired electrons. Hence, C₂H₂ is **diamagnetic**.

5. **Nitrogen dioxide (NO₂)**:
- Nitrogen (N) has 7 electrons, and Oxygen (O) has 8 electrons.
- Total electrons = 7 (N) + 2 × 8 (O) = 23 electrons.
- Since 23 is odd, there must be at least one unpaired electron.
- The Lewis structure of NO₂ shows that there is indeed one unpaired electron. Therefore, NO₂ is **paramagnetic**.

### Conclusion:
Among the given species, **Nitrogen dioxide (NO₂)** is the only paramagnetic species due to the presence of unpaired electrons.

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