# Chemical Bonding and Molecular Structure Notes | SwaVid Chemical Bonding and Molecular Structure, NCERT Class 11 Chemistry: notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-11/chemistry/chapter/chemical-bonding-and-molecular-structure Source: https://www.swavid.com/cbse/class-11/chemistry/chapter/chemical-bonding-and-molecular-structure # Chemical Bonding and Molecular Structure ## Formulas and definitions ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 11 Chemistry on SwaVid ### Kössel-Lewis approach and octet rule ### Ionic bonding and lattice enthalpy ### Bond parameters and dipole moment ### VSEPR theory ### Valence bond theory and hybridisation ### Molecular orbital theory ### Hydrogen bonding ### Next chapter ### Related chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 11 › Chemistry › Chemical Bonding and Molecular Structure Notes written by SwaVid from the NCERT textbook. Class 11 Chemistry, Unit 4. Key ideas, formulas and common mistakes. CBSE prints 7 marks for Unit 4, not for this chapter alone. Short answer. This chapter explains why atoms combine to form molecules and how various models describe chemical bonds. It builds an understanding of molecular shapes, bond polarity, orbital overlap, and molecular orbital theory. Source: NCERT Chemistry Part I (Reprint 2026-27) , Unit 4, Chemical Bonding and Molecular Structure Atoms combine either by transfer of valence electrons or by sharing them to achieve a stable octet of electrons. Lewis dot structures represent valence electrons, and formal charge helps select the most stable structure among resonance forms. Ionic bonds form easily between elements with low ionisation enthalpy and high negative electron gain enthalpy. Lattice enthalpy is the energy required to completely separate one mole of a solid ionic compound into gaseous constituent ions. Covalent bonds are characterised by bond length, bond angle, bond enthalpy, and bond order. Dipole moment measures the polarity of a bond or molecule, defined as the product of the magnitude of the charge and the distance of separation. The Valence Shell Electron Pair Repulsion theory predicts molecular geometry based on minimisation of repulsions between electron pairs. Repulsion decreases in the order: lone pair - lone pair > lone pair - bond pair > bond pair - bond pair. Valence bond theory describes covalent bonds through directional orbital overlap, producing stronger sigma bonds along the internuclear axis and weaker pi bonds sideways. Atomic orbitals mix to form equivalent hybrid orbitals like sp, sp², and sp³ to explain observed molecular shapes. Atomic orbitals combine linearly to form bonding and antibonding molecular orbitals spread over the entire molecule. Bond order is calculated from bonding and antibonding electron counts, determining bond stability and magnetic behaviour. An attractive force forms between a hydrogen atom covalently bonded to a strongly electronegative atom and another electronegative atom. It occurs either as intermolecular hydrogen bonding between different molecules or as intramolecular hydrogen bonding within the same molecule. Try each question first. Then tap it to see the answer. Valence electrons for oxygen atom V = 6 Non-bonding electrons on central oxygen L = 2 Bonding shared electrons on central oxygen S = 6 Formal charge = 6 - 2 - (1/2)(6) = 4 - 3 = +1 +1 Electron configuration: σ1s² σ*1s² σ2s² σ*2s² σ2p z ² π2p x ² π2p y ² π*2p x ¹ π*2p y ¹ Number of bonding electrons N b = 10 Number of antibonding electrons N a = 6 Bond order = (1/2)(10 - 6) = 2 Two unpaired electrons are present in π*2p orbitals, making it paramagnetic. Bond order = 2, paramagnetic Valence electrons of phosphorus = 5 Number of sigma bonds with chlorine atoms = 5 Number of lone pairs on phosphorus = 0 Total electron pairs = 5, which corresponds to sp³d hybridisation. Arrangement of 5 bonding pairs gives a trigonal bipyramidal geometry. sp³d, trigonal bipyramidal Thermodynamics . Structure of Atom . Classification of Elements and Periodicity in Properties . Organic Chemistry - Some Basic Principles and Techniques . The 9 chapters of Class 11 Chemistry . CBSE does not give marks to one chapter. It prints 7 marks for Unit 4, Chemical Bonding and Molecular Structure, which includes Chemical Bonding and Molecular Structure. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Thermodynamics. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Unit 4 NCERT book - 7 marks, Unit 4 - 3 quick checks - Confusing molecular geometry with electron pair geometry . Electron pair geometry considers both lone pairs and bond pairs, whereas molecular shape describes only the arrangement of the bonded atoms. - Using the same MO energy level sequence for all homonuclear diatomic molecules . Use the sequence with σ2p z lower in energy than π2p only for O₂ and F₂. For B₂, C₂, and N₂, place the degenerate π2p orbitals lower in energy than σ2p z . - Assuming all molecules with polar bonds have a net dipole moment . Check the molecular symmetry because individual bond dipoles are vectors that can cancel each other out, as in CO₂ and CCl₄. - Counting a double bond as two separate electron pairs in VSEPR theory . Treat multiple bonds, whether double or triple, as a single super-pair when determining the steric number and spatial geometry in VSEPR. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 11](https://www.swavid.com/cbse/class-11) - [Chemistry](https://www.swavid.com/cbse/class-11/chemistry/chapters) - [Start free →](https://www.swavid.com/signup) - [All 9 chapters](https://www.swavid.com/cbse/class-11/chemistry/chapters) - [NCERT Chemistry Part I (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-11/chemistry/chapter/thermodynamics) - [Open notes](https://www.swavid.com/cbse/class-11/chemistry/chapter/structure-of-atom) - [Open notes](https://www.swavid.com/cbse/class-11/chemistry/chapter/classification-of-elements-and-periodicity-in-properties) - [Open notes](https://www.swavid.com/cbse/class-11/chemistry/chapter/organic-chemistry-some-basic-principles-and-techniques) - [Class 11 Chemistry](https://www.swavid.com/cbse/class-11/chemistry/chapters) - [Start free →](https://www.swavid.com/signup)