Question

Which among the following halides has trigonal bipyramidal structure?

• A. $\text{SeCl}_2$
• B. $\text{SeF}_4$
• C. $\text{SF}_6$
• D. $\text{TeF}_6$

Hint:

Any stable neutral interhalogen or chalcogen halide containing a central Group 16 atom bound to exactly 4 monovalent halide ligands ($\text{EX}_4$ type like $\text{SF}_4$ or $\text{SeF}_4$) features 4 bonding pairs and 1 lone pair. This total of 5 electron domains always maps to a trigonal bipyramidal electron geometry framework.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks us to identify the compound from the given molecular halides that possesses or is based upon a trigonal bipyramidal electron geometry framework via Valence Shell Electron Pair Repulsion (VSEPR) theory.

Step 2: Key Formula or Approach:
Determine the steric number (SN) of the central atom using the valence formula: $$\text{SN} = \frac{1}{2} \times [V + M - C + A]$$ where $V$ is valence electrons of the central atom, $M$ is the number of monovalent atoms, $C$ is cationic charge, and $A$ is anionic charge. A steric number of 5 corresponds to a trigonal bipyramidal basic electron-pair geometry.

Step 3: Detailed Explanation:
Let's analyze the steric parameters of the given choices: 1.

$\text{SeCl}_2$: Selenium has 6 valence electrons, $+2$ monovalent chlorines = 8 electrons (4 pairs). $\text{SN} = 4$ ($\text{sp}^3$ hybridization, bent molecular shape based on tetrahedral geometry).
2.

$\text{SeF}_4$: Selenium has 6 valence electrons, $+4$ monovalent fluorines = 10 electrons (5 pairs). $\text{SN} = 5$. This requires $\text{sp}^3\text{d}$ hybridization, yielding a trigonal bipyramidal electron-pair geometry (with one lone pair creating a see-saw molecular shape).
3.

$\text{SF}_6$: Sulfur has 6 valence electrons, $+6$ fluorines = 12 electrons (6 pairs). $\text{SN} = 6$ ($\text{sp}^3\text{d}^2$ hybridization, octahedral structure).
4.

$\text{TeF}_6$: Tellurium also belongs to group 16, giving it 6 valence electrons, $+6$ fluorines = 12 electrons (6 pairs). $\text{SN} = 6$ ($\text{sp}^3\text{d}^2$ hybridization, octahedral structure).
Therefore, $\text{SeF}_4$ is the only molecule based on the trigonal bipyramidal arrangement.

Step 4: Final Answer:
The halide that has a trigonal bipyramidal structural arrangement is $\text{SeF}_4$, which corresponds to option (B).