The species which is paramagnetic

Options

A. `Cr^(+)`
B. `Zn^(2+)`
C. `Cu^(+)`
D. `MnO_(4)`

Answer

To determine which of the given species is paramagnetic, we need to analyze the electronic configurations of each species and identify the presence of unpaired electrons. A species is considered paramagnetic if it has one or more unpaired electrons.

### Step-by-Step Solution:

1. **Identify the Species:**
We have four options to analyze:
- Option 1: Chromium (Cr⁺)
- Option 2: Zinc (Zn²⁺)
- Option 3: Copper (Cu⁺)
- Option 4: Manganate ion (MnO₄⁻)

2. **Analyze Chromium (Cr⁺):**
- The electronic configuration of neutral chromium (Cr) is:
\[ \text{Cr: } [\text{Ar}] 3d^5 4s^1 \]
- For Cr⁺, we remove one electron (from the 4s orbital):
\[ \text{Cr}^+: [\text{Ar}] 3d^5 4s^0 \]
- The 3d subshell has 5 electrons, all of which are unpaired (due to Hund's rule).
- **Conclusion:** Cr⁺ is paramagnetic (5 unpaired electrons).

3. **Analyze Zinc (Zn²⁺):**
- The electronic configuration of neutral zinc (Zn) is:
\[ \text{Zn: } [\text{Ar}] 4s^2 3d^{10} \]
- For Zn²⁺, we remove two electrons (from the 4s orbital):
\[ \text{Zn}^{2+}: [\text{Ar}] 3d^{10} 4s^0 \]
- The 3d subshell has 10 electrons, all of which are paired.
- **Conclusion:** Zn²⁺ is not paramagnetic (no unpaired electrons).

4. **Analyze Copper (Cu⁺):**
- The electronic configuration of neutral copper (Cu) is:
\[ \text{Cu: } [\text{Ar}] 3d^{10} 4s^1 \]
- For Cu⁺, we remove one electron (from the 4s orbital):
\[ \text{Cu}^+: [\text{Ar}] 3d^{10} 4s^0 \]
- The 3d subshell has 10 electrons, all of which are paired.
- **Conclusion:** Cu⁺ is not paramagnetic (no unpaired electrons).

5. **Analyze Manganate Ion (MnO₄⁻):**
- To find the oxidation state of manganese (Mn) in MnO₄⁻, we set up the equation:
\[ X + 4(-2) = -1 \]
\[ X - 8 = -1 \]
\[ X = +7 \]
- The electronic configuration of neutral manganese (Mn) is:
\[ \text{Mn: } [\text{Ar}] 3d^5 4s^2 \]
- For Mn⁷⁺, we remove 7 electrons (5 from 3d and 2 from 4s):
\[ \text{Mn}^{7+}: [\text{Ar}] 3d^0 4s^0 \]
- There are no electrons left in the d or s orbitals.
- **Conclusion:** MnO₄⁻ is not paramagnetic (no unpaired electrons).

### Final Conclusion:
The only species that is paramagnetic is **Chromium (Cr⁺)**, which has 5 unpaired electrons.