Which of the following species has polar and non-polar bonds but molecule as a whole is non-plonar?

Options

A. `S_(2)O_(3)^(2-)`
B. `(SCN)_(2)`
C. `Be_(2)Cl_(4)`
D. `Si_(2)H_(6)`

Explanation

To determine which of the given species has polar and non-polar bonds but is non-polar as a whole molecule, we need to analyze each option step by step.

### Step 1: Analyze the first species, \( S_2O_3^{2-} \)

1. **Structure**: The structure consists of a double bond between two sulfur atoms and single bonds to three oxygen atoms.
2. **Bond Polarity**:
- The S-S bond is non-polar because both sulfur atoms have the same electronegativity.
- The S-O bonds are polar because oxygen is more electronegative than sulfur, leading to a partial negative charge on oxygen and a partial positive charge on sulfur.
3. **Overall Polarity**: The molecule has both polar and non-polar bonds, but due to the symmetrical arrangement of the bonds, the overall molecule is non-polar.

### Step 2: Analyze the second species, \( SCN^{2-} \)

1. **Structure**: The structure includes two sulfur atoms connected by a single bond, with a cyanide (C≡N) group attached.
2. **Bond Polarity**:
- The S-S bond is non-polar.
- The C≡N bond is polar due to the difference in electronegativity between carbon and nitrogen.
3. **Overall Polarity**: The molecule has both polar and non-polar bonds, but the arrangement is not symmetrical, leading to a net dipole moment. Thus, this molecule is polar.

### Step 3: Analyze the third species, \( BeCl_2 \)

1. **Structure**: The structure consists of a beryllium atom bonded to two chlorine atoms.
2. **Bond Polarity**:
- Both Be-Cl bonds are polar due to the electronegativity difference between beryllium and chlorine.
3. **Overall Polarity**: The molecule is linear, and the dipoles cancel each other out, making the overall molecule non-polar. However, it does not contain non-polar bonds, so it does not satisfy the question's criteria.

### Step 4: Analyze the fourth species, \( Si_2H_6 \)

1. **Structure**: The structure consists of two silicon atoms bonded to six hydrogen atoms.
2. **Bond Polarity**:
- The Si-Si bond is non-polar.
- The Si-H bonds are polar because silicon is less electronegative than hydrogen.
3. **Overall Polarity**: The molecule has both polar and non-polar bonds, but due to the symmetrical arrangement, the overall molecule is non-polar.

### Conclusion

After analyzing all four species, we find that:

- **Option 1** \( S_2O_3^{2-} \): Non-polar overall.
- **Option 2** \( SCN^{2-} \): Polar overall.
- **Option 3** \( BeCl_2 \): Non-polar overall but has only polar bonds.
- **Option 4** \( Si_2H_6 \): Non-polar overall.

The correct answer is **Option 1** \( S_2O_3^{2-} \) as it has both polar and non-polar bonds and is non-polar as a whole molecule.