Amongst the following, the total number of species NOT having eight electrons around central atom in its outer most shell, is NH3, AICI3, BeCl2, CCl4, PCI5 :
2
4
1
3
The Correct Option is D
Solution and Explanation
Let's analyze each species:
NH3 (Ammonia): Nitrogen (N) has 5 valence electrons. In NH3, there are three shared electron pairs around nitrogen (one from each hydrogen atom). The total number of electrons around the central nitrogen atom is 3 x 2 (shared pairs) + 2 (non-bonding pair) = 8. So, NH3 has eight electrons around the central atom.
AlCl3 (Aluminum trichloride): Aluminum (Al) has 3 valence electrons, and chlorine (Cl) has 7 valence electrons each. In AlCl3, aluminum forms three bonds with chlorine, and each chlorine atom has 3 lone pairs. The total number of electrons around the central aluminum atom is 3 x 2 (shared pairs) + 6 (non-bonding pairs) = 12. So, AlCl3 does not have eight electrons around the central atom.
BeCl2 (Beryllium dichloride): Beryllium (Be) has 2 valence electrons, and chlorine (Cl) has 7 valence electrons each. In BeCl2, beryllium forms two bonds with chlorine, and each chlorine atom has 3 lone pairs. The total number of electrons around the central beryllium atom is 2 x 2 (shared pairs) + 6 (non-bonding pairs) = 10. So, BeCl2 does not have eight electrons around the central atom.
CCl4 (Carbon tetrachloride): Carbon (C) has 4 valence electrons, and chlorine (Cl) has 7 valence electrons each. In CCl4, carbon forms four bonds with chlorine. The total number of electrons around the central carbon atom is 4 x 2 (shared pairs) = 8. So, CCl4 has eight electrons around the central atom.
PCl5 (Phosphorus pentachloride): Phosphorus (P) has 5 valence electrons, and chlorine (Cl) has 7 valence electrons each. In PCl5, phosphorus forms five bonds with chlorine. The total number of electrons around the central phosphorus atom is 5 x 2 (shared pairs) = 10. So, PCl5 does not have eight electrons around the central atom.
Now, let's count the species that do not have eight electrons around the central atom:
AlCl3, BeCl2, PCl5 (3 species)
The correct answer is (D): 3.
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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