Question

In the structure of ClF₃ , the number of lone pairs of electrons on central atom ‘Cl’ is

• A. one
• B. four
• C. two
• D. three

Answer 1

The Correct Option is C

To determine the number of lone pairs of electrons on the central atom in the molecule ClF₃, we need to analyze its Lewis structure and apply the Valence Shell Electron Pair Repulsion (VSEPR) theory.

1. Determine the total number of valence electrons:
   Chlorine (Cl) is in group 17 and has 7 valence electrons.
   Each fluorine (F) atom also has 7 valence electrons, and there are 3 fluorine atoms in ClF₃.
   Total valence electrons = 7 (from Cl) + 3 × 7 (from F) = 7 + 21 = 28 electrons.
2. Construct the Lewis structure:
   ClF₃ primary structure is a central chlorine atom bonded to three fluorine atoms.
   Initially, use 6 electrons to form bonds to three fluorine atoms (3 bonds × 2 electrons per bond = 6 electrons).
   Remaining electrons = 28 total electrons - 6 bonding electrons = 22 electrons.
   Distribute the remaining 22 electrons as lone pairs. Each fluorine requires 6 more to complete the octet:
   • Place 6 electrons (3 lone pairs) on each F atom, totaling 18 electrons (3 F × 6 electrons) for the fluorine atoms.
   • This leaves 4 electrons, which are placed on the central chlorine atom as lone pairs.
3. Identify lone pairs on the central chlorine atom:
   Two lone pairs remain on chlorine after accounting for bonds and fulfilling the octet of fluorines.
4. Apply VSEPR theory:
   With 3 bonded pairs and 2 lone pairs, ClF₃ has a trigonal bipyramidal electron pair geometry.
   Lone pairs occupy equatorial positions, minimizing their interference with bonds, resulting in a T-shaped molecule.
5. Conclusion:
   The number of lone pairs of electrons on the central atom 'Cl' is two.