Question

Given are 4 pairs of covalent molecules. Identify the pair in which both molecules have the same shape.

• A. XeF\(_2\) and HgCl\(_2\)
• B. BF\(_3\) and NH\(_3\)
• C. XeF\(_4\) and SF\(_4\)
• D. BrF\(_5\) and PCl\(_5\)

Hint:

The VSEPR theory can be used to predict the shape of molecules by considering the number of bonding pairs and lone pairs around the central atom. Linear geometry occurs when there are 2 bonding pairs and no lone pairs or when lone pairs cause repulsion to maintain a linear shape.

Answer 1

The Correct Option is A

Step 1: Analyze the shape of XeF\(_2\).
XeF\(_2\) is a molecule with 2 fluorine atoms bonded to xenon, and there are 3 lone pairs of electrons on the xenon atom. According to the VSEPR theory, this leads to a linear shape for XeF\(_2\), as the lone pairs are arranged in a way that minimizes electron-electron repulsion, resulting in a 180° bond angle.

Step 2: Analyze the shape of HgCl\(_2\).
HgCl\(_2\) is a molecule with 2 chlorine atoms bonded to mercury. Mercury in this molecule follows the VSEPR theory and similarly adopts a linear geometry, as there are no lone pairs on mercury, and the two bonding pairs of electrons are arranged linearly.

Step 3: Conclusion.
Both XeF\(_2\) and HgCl\(_2\) have a linear geometry, meaning they share the same molecular shape. Thus, option (A) is correct.

Step 4: Conclusion for other options.
- In option (B), BF\(_3\) has a trigonal planar shape, while NH\(_3\) has a trigonal pyramidal shape. Therefore, they don't have the same shape.
- In option (C), XeF\(_4\) has a square planar shape, while SF\(_4\) has a see-saw shape. Therefore, they don't have the same shape.
- In option (D), BrF\(_5\) has a square pyramidal shape, while PCl\(_5\) has a trigonal bipyramidal shape. Therefore, they don't have the same shape.

Step 5: Final Answer.
Therefore, the correct answer is option (A).