Which pair of the following compounds has one lone pair of electrons on the central atom?

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Accepted Answer

1. **Method:** To find the number of lone pairs on the central atom, calculate the valence electrons remaining after bond formation. Lone Pairs = (Valence electrons of central atom - Valency of surrounding atoms) / 2.
2. **Analyze SF$$_4$$:** Sulfur (Group 16) has 6 valence electrons. It forms 4 sigma bonds with Fluorine. Remaining electrons = $$6 - 4 = 2$$. Thus, it has **1 lone pair** .
3. **Analyze BrF$$_5$$:** Bromine (Group 17) has 7 valence electrons. It forms 5 sigma bonds with Fluorine. Remaining electrons = $$7 - 5 = 2$$. Thus, it has **1 lone pair** .
4. **Analyze ClF$$_3$$:** Chlorine (Group 17) has 7 valence electrons. It forms 3 sigma bonds with Fluorine. Remaining electrons = $$7 - 3 = 4$$. Thus, it has **2 lone pairs** .
5. **Analyze XeF$$_4$$:** Xenon (Group 18) has 8 valence electrons. It forms 4 sigma bonds with Fluorine. Remaining electrons = $$8 - 4 = 4$$. Thus, it has **2 lone pairs** .
6. **Conclusion:** Both SF$$_4$$ and BrF$$_5$$ have exactly one lone pair on the central atom.

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