Chemical Bonding and Molecular Structure
Class 11 · Chemistry
4 ideas in Class 11 Chemistry, explained in plain words, with games and quizzes to practise.
Ionic and Covalent Bonds
Part of: Bonds and Their Measures
Electron transfer builds ion lattices glued by lattice energy; sharing builds molecules. Big pull gaps go ionic, small gaps stay covalent, and unequal sharing turns polar. Melts free ions to carry current that solids lock away.
Why it matters. Bond type predicts melting, conduction and solubility. Gap size is the quickest classifier.
Formulas
- Overall formation = transfer cost minus lattice payoff.
- Big pull gaps go ionic; small gaps stay covalent.
Key words
- Ionic bond
- : Electron transfer building ion lattices.
- Covalent bond
- : Electron sharing between atoms.
- Polar covalent
- : Unequal sharing from a pull gap.
- Lattice energy
- : Packing payoff gluing an ion lattice.
Try it in two minutes
- Test salt versus sugar melts and solutions.
- Rank three pairs by pull gaps.
- Melt wax and note non-conduction.
Try at home. Compare salt and sugar in water conduction.
Bond Parameters and Polarity
Part of: Bonds and Their Measures
Higher order shortens and strengthens bonds. Enthalpy differences price reactions. Dipoles multiply charge by separation; shapes can cancel them as in linear carbon dioxide. Lone pairs squeeze angles below ideal, and formal charges audit electron books.
Why it matters. Numbers turn sketches into predictions: strength, polarity and shape all follow.
Formulas
- Reaction enthalpy = bonds broken minus bonds formed.
- Formal charge = valence minus (lone electrons + bonds).
- Percent ionic = observed dipole x 100 / full-charge dipole.
Key words
- Bond order
- : Single, double or triple link count.
- Bond enthalpy
- : Strength priced in energy; larger means stronger.
- Dipole moment
- : Charge times separation.
- Formal charge
- : Electron bookkeeping on each atom.
- Lone pair squeeze
- : Lone pairs squeezing angles below ideal.
Try it in two minutes
- Rank single, double, triple by length.
- Price a reaction from bond enthalpies.
- Cancel arrows in a linear molecule.
Try at home. Compare ball-and-stick angles with ideal ones.
VSEPR and Hybridization
Part of: Shapes, Orbitals and Weak Bonds
Electron pairs arrange to minimise repulsion: lone pairs demand most room, then bonds. Counts set geometry from linear to octahedral. Matching atomic orbitals blend into hybrids: two regions sp, three sp2, four sp3, five sp3d, six sp3d2.
Why it matters. Shape decides polarity, reactivity and function. Counting regions predicts geometry without memorising each molecule.
Formulas
- Regions 2, 3, 4 give sp, sp2, sp3.
- Regions 5, 6 give sp3d, sp3d2.
Key words
- VSEPR
- : Pairs arrange to minimise repulsion.
- Steric number
- : Bond plus lone pair count setting geometry.
- Hybridization
- : Atomic orbitals blending to match the count.
- Tetrahedral
- : Four-region shape with 109.5-degree angles.
- Lone pair effect
- : Lone pairs demand most room and bend shapes.
Try it in two minutes
- Count regions around five molecules.
- Match counts with shapes.
- Assign hybrids to each count.
Try at home. Build balloon pair models for each count.
Molecular Orbitals and Hydrogen Bonding
Part of: Shapes, Orbitals and Weak Bonds
Atomic orbitals merge into lower bonding and higher antibonding sets; half the difference is bond order, and unpaired electrons magnetise. Hydrogen bonds bridge hydrogen to small electronegative atoms, lifting boiling points and floating ice on an open lattice.
Why it matters. Bond orders explain oxygen's magnetism and nitrogen's laziness. Hydrogen bonds run water, proteins and DNA.
Formulas
- Bond order = (bonding - antibonding) / 2
- Hydrogen bonds lift boiling points and float ice.
Key words
- Molecular orbital
- : Merged atomic sets, lower bonding and higher antibonding.
- Antibonding orbital
- : A higher merged set weakening the link.
- Orbital bond order
- : Half the difference of bonding and antibonding counts.
- Paramagnetic
- : Unpaired electrons magnetising the molecule.
- Hydrogen bond
- : A bridge from hydrogen to small electronegative atoms.
Try it in two minutes
- Fill orbital ladders for H2, O2, N2.
- Count unpaired electrons in each.
- Compare ammonia with phosphine boiling.
Try at home. Float ice and note the open structure.
What your child will practise
- Bond Parameters and Polarity: Desert Puzzle (Clue Puzzle)
- Bond Parameters and Polarity: Desert Quick Fire (Quick Fire)
- Ionic and Covalent Bonds: Space Puzzle (Clue Puzzle)
- Molecular Orbitals and Hydrogen Bonding: Space Quest (Flip and Match)
- VSEPR and Hybridization: Jungle Quick Fire (Quick Fire)
- Quiz: Bond Parameters and Polarity (8 questions)
- Quiz: Ionic and Covalent Bonds (8 questions)
- Quiz: Molecular Orbitals and Hydrogen Bonding (8 questions)
- Quiz: VSEPR and Hybridization (8 questions)