Question:

Number of lone pairs of electrons in the central atom of SCl2, O3, CIF3 and SF6, respectively, are:

Updated On: Dec 29, 2025
  • 0, 1, 2 and 2
  • 2, 1, 2 and 0
  • 1, 2, 2 and 0
  • 2, 1, 0 and 2
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The Correct Option is B

Approach Solution - 1

To determine the number of lone pairs of electrons on the central atom for each of the given molecules, we will evaluate the electronic configuration and geometry of each molecule. 

  1. SCl2:
    • Sulfur (S) belongs to Group 16 of the periodic table and has 6 valence electrons.
    • Each chlorine (Cl) atom, being a Group 17 element, forms a single bond with sulfur, using up 2 valence electrons from sulfur (1 for each Cl).
    • After forming two bonds with chlorine, sulfur has 4 valence electrons remaining, which are organized into 2 lone pairs.
    • The number of lone pairs on the central sulfur atom in SCl2 is 2.
  2. O3 (Ozone):
    • Ozone has a resonance structure consisting of one double bond and one single bond between oxygen atoms.
    • The central oxygen atom participates in both of these bonds.
    • Oxygen, having 6 valence electrons, after forming a double bond (using 2 electrons) and a single bond (using 1 electron), will have 3 electrons left, forming 1.5 electron pairs.
    • Typically, central oxygen can be pictured with one lone pair in most stable resonance forms.
    • The number of lone pairs on the central oxygen atom in O3 is 1.
  3. ClF3:
    • Chlorine (Cl) is the central atom with 7 valence electrons.
    • Three fluorine atoms each form a single bond with chlorine, using 3 electrons.
    • This leaves chlorine with 4 electrons, or 2 lone pairs.
    • The number of lone pairs on the central chlorine atom in ClF3 is 2.
  4. SF6:
    • Sulfur is the central atom with 6 valence electrons.
    • There are six fluorine atoms, each forming a single bond with sulfur, using up all 6 sulfur valence electrons, with no remaining electrons for lone pairs.
    • The number of lone pairs on the central sulfur atom in SF6 is 0.

Thus, the number of lone pairs of electrons on the central atom for SCl2, O3, ClF3, and SF6 respectively are 2, 1, 2, and 0. The correct option is: 2, 1, 2 and 0.

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Approach Solution -2

The number of lone pair of electrons in the central atom of SCl2, O3, CIF3 and SF6 are 2, 1, 2 and O respectively
Their structures are as,

Fig.

So, the correct option is (B): 2, 1, 2 and 0.

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Concepts Used:

Chemical Bonding and Molecular Structure

Such a group of atoms is called a molecule. Obviously, there must be some force that holds these constituent atoms together in the molecules. The attractive force which holds various constituents (atoms, ions, etc.) together in different chemical species is called a chemical bond.

Types of Chemical Bonds:

There are 4 types of chemical bonds which are formed by atoms or molecules to yield compounds. 

  • Ionic Bonds - Ionic bonding is a type of chemical bonding which involves a transfer of electrons from one atom or molecule to another.
  • Covalent Bonds - Compounds that contain carbon commonly exhibit this type of chemical bonding. 
  • Hydrogen Bonds -  It is a type of polar covalent bonding between oxygen and hydrogen wherein the hydrogen develops a partial positive charge
  • Polar Bonds - In Polar Covalent chemical bonding, electrons are shared unequally since the more electronegative atom pulls the electron pair closer to itself and away from the less electronegative atom.

Factors Affecting Bond Enthalpy in Chemical Bonding:

  • Size of the Atom
  • Multiplicity of Bonds
  • Number of Lone Pair of Electrons Present
  • Bond Angle