Question

Which one of the following compounds is having maximum 'lone pair-lone pair' electron repulsions?

• A. ClF\(_3\)
• B. IF\(_5\)
• C. SF\(_4\)
• D. XeF\(_2\)

Hint:

Lone pair-lone pair repulsion is strongest when lone pairs are in positions where they are not spread out, such as the axial positions in square pyramidal or linear geometries.

Answer 1

The Correct Option is D

Step 1: {Understanding Lone Pair-Lone Pair Repulsions}
Lone pairs of electrons on the central atom experience repulsion from each other. The maximum repulsion occurs when the lone pairs are placed in positions that minimize their mutual interaction. The lone pair-lone pair repulsion increases with the number of lone pairs and the spatial arrangement. Step 2: {Analysis of Compounds}
In ClF\(_3\), there are 3 lone pairs on the central chlorine atom and 2 bonding pairs, with a T-shaped geometry.
In IF\(_5\), there are 2 lone pairs on iodine and 5 bonding pairs, with a square pyramidal geometry.
In SF\(_4\), there is 1 lone pair on the sulfur atom and 4 bonding pairs, with a seesaw geometry.
In XeF\(_2\), there are 3 lone pairs on the central xenon atom and 2 bonding pairs, with a linear geometry.
Since XeF\(_2\) has the most lone pairs (3), the lone pair-lone pair repulsions are the highest, and hence, XeF\(_2\) experiences the maximum repulsion.
Thus, the correct answer is (D).

Answer 2

Step 1: Understand the concept of lone pair-lone pair (lp-lp) repulsion
Electron pair repulsions are based on VSEPR (Valence Shell Electron Pair Repulsion) theory.
Repulsions follow this order in decreasing strength:
Lone pair–lone pair (lp-lp) > Lone pair–bond pair (lp-bp) > Bond pair–bond pair (bp-bp)
Thus, molecules with more lone pairs on the central atom will have higher lp-lp repulsions.

Step 2: Analyze the given compounds
We compare compounds based on the number of lone pairs on the central atom.
Let’s consider the electron pair geometry around each central atom:

Option: XeF₂
- Central atom: Xenon (Xe)
- Total valence electrons = 8 (Xe) + 2×7 (F) = 22 electrons
- Bonding pairs = 2 (from 2 F atoms)
- Remaining = 6 electrons = 3 lone pairs on Xe
- Geometry: Trigonal bipyramidal (with 3 equatorial lone pairs)
- Maximum lp-lp repulsions due to 3 lone pairs

Other typical comparisons:
- SF₄: 1 lone pair on sulfur
- IF₅: 1 lone pair on iodine
- BrF₃: 2 lone pairs on bromine
Among these, XeF₂ has the highest number of lone pairs

Step 3: Final answer
Maximum lone pair-lone pair repulsions are present in:
XeF₂