Class 11 Chemistry - HARYANA
Chemical Bonding and Molecular Structure
Chemical Bonding and Molecular Structure is a fundamental chapter in Class 11 Chemistry that explains why and how atoms combine to form molecules. As prescribed by the Haryana Board (BSEH), this chapter covers crucial theories like Kossel-Lewis approach, VSEPR theory, Valence Bond Theory (VBT), and Molecular Orbital Theory (MOT). Understanding hybridization, dipole moment, and hydrogen bonding is essential not only for scoring high in board exams but also for building a strong base for organic and inorganic chemistry in higher classes.
Start Learning FreeKey Concepts
Octet Rule
Atoms tend to combine so that each has eight electrons in its valence shell, giving them a stable electronic configuration like noble gases.
VSEPR Theory
Valence Shell Electron Pair Repulsion theory states that electron pairs around a central atom repel each other, determining the 3D geometry of molecules.
Hybridization
The process of mixing atomic orbitals of comparable energies to form new hybridized orbitals of equivalent energy and shape, such as sp, sp2, and sp3.
Molecular Orbital Theory (MOT)
Explains bonding by combining atomic orbitals to form bonding and antibonding molecular orbitals, helping determine bond order and magnetic behavior.
Hydrogen Bonding
A special type of dipole-dipole attraction between a hydrogen atom bonded to a strongly electronegative atom (like F, O, N) and another electronegative atom.
Important Formulas
Board Exam Info
In the Haryana Board (BSEH) Class 11 Chemistry examination, this chapter typically carries around 5 to 7 marks. Questions commonly include drawing Lewis structures, predicting shapes of molecules using VSEPR theory, explaining hybridization of central atoms, and calculating bond orders using Molecular Orbital Theory.
Frequently Asked Questions
Why is the bond angle in water (H2O) less than the tetrahedral angle (109.5°)?
According to VSEPR theory, lone pair-lone pair repulsion is greater than lone pair-bond pair repulsion, which in turn is greater than bond pair-bond pair repulsion. Water has two lone pairs on the oxygen atom, which push the hydrogen-oxygen bonds closer together, reducing the bond angle to 104.5°.
What is the difference between sigma (σ) and pi (π) bonds?
Sigma bonds are formed by the end-to-end (axial) overlapping of atomic orbitals and are strong. Pi bonds are formed by lateral (sideways) overlapping of atomic orbitals and are weaker than sigma bonds.
How can we determine if a molecule is paramagnetic or diamagnetic using MOT?
If all molecular orbitals are fully paired with electrons, the substance is diamagnetic. If there is at least one unpaired electron in the molecular orbitals, the substance is paramagnetic.
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