Number of compounds with one lone pair of electrons on central atom amongst following is
\(CIF_3, XeO_3, BrF_5, XeF_4, O_3, NH_3\),\( H_2O\)
\(CIF_3, XeO_3, BrF_5, XeF_4, O_3, NH_3\),\( H_2O\)
Correct Answer: 4
Approach Solution - 1
1. CIF₃ (Chlorine trifluoride)
Chlorine (Cl) has 7 valence electrons. It forms 3 bonds with F atoms → uses 3 electrons. Remaining = 7 – 3 = 4 electrons = 2 lone pairs.
→ **2 lone pairs on Cl**
2. XeO₃ (Xenon trioxide)
Xenon (Xe) has 8 valence electrons. Each oxygen forms a double bond, using 6 electrons in total (3 × 2). Used 6 electrons → 8 – 6 = 2 electrons = 1 lone pair.
→ **1 lone pair on Xe**
3. BrF₅ (Bromine pentafluoride)
Bromine (Br) has 7 valence electrons. Forms 5 bonds with F → uses 5 electrons. Remaining 7 – 5 = 2 electrons = 1 lone pair.
→ **1 lone pair on Br**
4. XeF₄ (Xenon tetrafluoride)
Xenon (Xe) has 8 valence electrons. Forms 4 bonds with F → uses 4 electrons. Remaining 8 – 4 = 4 electrons = 2 lone pairs.
→ **2 lone pairs on Xe**
5. O₃ (Ozone)
Central O has 6 valence electrons. It forms one single and one double bond (resonance). Bonds use 3 pairs = 6 electrons → 6 – 4 = 2 electrons = 1 lone pair.
→ **1 lone pair on central O**
6. NH₃ (Ammonia)
Nitrogen has 5 valence electrons. Forms 3 bonds with H → uses 3 electrons. Remaining 2 electrons = 1 lone pair.
→ **1 lone pair on N**
7. H₂O (Water)
Oxygen has 6 valence electrons. Forms 2 bonds with H → uses 2 electrons. Remaining 4 electrons = 2 lone pairs.
→ **2 lone pairs on O**
Step 5: Count of Compounds with One Lone Pair
Compounds with exactly one lone pair on central atom: \[ \text{XeO}_3, \; \text{BrF}_5, \; \text{O}_3, \; \text{NH}_3 \] Total = **4**
Final Answer:
\[ \boxed{4} \]
Approach Solution -2
To determine the number of compounds with one lone pair on the central atom, let’s examine each compound:
- O3: Contains one lone pair on the central oxygen atom.
- H2O: Contains two lone pairs on the central oxygen atom.
- SF4: Contains one lone pair on the sulfur atom.
- ClF3: Contains two lone pairs on the chlorine atom.
- NH3: Contains one lone pair on the nitrogen atom.
- BrF5: Contains one lone pair on the bromine atom.
- XeF4: Contains two lone pairs on the xenon atom.
From the above, the compounds with exactly one lone pair on the central atom are: O3, SF4, NH3, and BrF5.
Total: 4 Compounds
So, the correct answer is: 4
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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