Class 11 Chemistry - CBSE
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. It covers essential theories like VSEPR, Valence Bond Theory, and Molecular Orbital Theory to predict the shapes, geometry, and magnetic behavior of compounds. Mastery of hybridization, dipole moment, and hydrogen bonding is crucial for understanding chemical reactivity. For CBSE board exams, this chapter is high-scoring and forms the backbone of organic and inorganic chemistry, typically contributing 5 to 7 marks with a mix of conceptual reasoning, structure drawing, and numerical-based bond order questions.
Start Learning FreeKey Concepts
Octet Rule
Atoms tend to combine so that each has eight electrons in its valence shell, achieving a stable noble gas configuration.
VSEPR Theory
Valence Shell Electron Pair Repulsion theory states that electron pairs around a central atom repel each other, determining the 3D molecular shape.
Hybridization
The concept of mixing atomic orbitals of comparable energies to form new hybridized orbitals of equivalent energy and specific geometry.
Molecular Orbital Theory
Describes bonding as the combination of atomic orbitals to form molecular orbitals, explaining magnetic properties and bond stability.
Hydrogen Bonding
A strong dipole-dipole attraction between a hydrogen atom bonded to a highly electronegative atom (F, O, N) and another electronegative atom.
Important Formulas
Board Exam Info
In the CBSE Class 11 Chemistry exam, this chapter generally carries about 5 to 7 marks. Common question types include predicting shapes of molecules using VSEPR theory, drawing Lewis structures, calculating formal charge and bond order, explaining hybridization of central atoms, and conceptual reasoning questions on dipole moment and hydrogen bonding.
Frequently Asked Questions
Water has two lone pairs and two bond pairs on the central oxygen atom. According to VSEPR theory, lone pair-lone pair repulsion is greater than lone pair-bond pair repulsion, which pushes the bond pairs closer and reduces the bond angle to approximately 104.5 degrees.
Polarity depends on the presence of polar bonds and the symmetrical or asymmetrical shape of the molecule. If the individual bond dipoles do not cancel each other out vectorially, the molecule is polar (e.g., NH3); if they cancel out, it is non-polar (e.g., CO2).
A sigma bond is formed by the end-to-end (axial) overlap of atomic orbitals and allows free rotation, whereas a pi bond is formed by lateral (sideways) overlap and restricts rotation around the bond axis.
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