Question

The number of lone pairs of electrons on the central atom of \( ClF_3, NF_3, SF_4, XeF_4 \) respectively are?

• A. \( 0,1,0,2 \)
• B. \( 2,1,0,0 \)
• C. \( 2,1,1,2 \)
• D. \( 2,1,1,0 \)

Hint:

To determine lone pairs on a central atom, use the VSEPR theory and subtract the bonding pairs from the total valence electrons. The remaining pairs are lone pairs.

Answer 1

The Correct Option is C

To determine the number of lone pairs on the central atom in each molecule, we use the Valence Shell Electron Pair Repulsion (VSEPR) Theory. Step 1: Lone Pairs in \( ClF_3 \) 
- Chlorine (Cl) has 7 valence electrons.
- Fluorine atoms use 3 bonding pairs, leaving 2 lone pairs.
- Molecular geometry: T-shaped.
Thus, the lone pairs on \( ClF_3 \) = 2.
Step 2: Lone Pairs in \( NF_3 \) 
- Nitrogen (N) has 5 valence electrons.
- Three fluorine atoms form 3 bonding pairs, leaving 1 lone pair.
- Molecular geometry: Trigonal pyramidal.
Thus, the lone pairs on \( NF_3 \) = 1. 

Step 3: Lone Pairs in \( SF_4 \) 
- Sulfur (S) has 6 valence electrons.
- Four fluorine atoms form 4 bonding pairs, leaving 1 lone pair.
- Molecular geometry: Seesaw.
Thus, the lone pairs on \( SF_4 \) = 1.
Step 4: Lone Pairs in \( XeF_4 \) 
- Xenon (Xe) has 8 valence electrons.
- Four fluorine atoms form 4 bonding pairs, leaving 2 lone pairs.
- Molecular geometry: Square planar.
Thus, the lone pairs on \( XeF_4 \) = 2.
Step 5: Verify the Correct Answer 
From our calculations, the number of lone pairs on the central atoms is \( 2,1,1,2 \), which matches Option (3).