135 articles
Bonding & Molecular Structure
Ionic, covalent and metallic bonds, molecular shapes, intermolecular forces and naming compounds.
Hydrogen Bonding in DNA and Proteins
How hydrogen bonds hold DNA's base pairs together and shape proteins: donors and acceptors in A–T and G–C, why strands can separate, α-helices and β-sheets, and why weak bonds are ideal for biology.
Intermolecular Forces Practice Questions
15 exam-style questions on London forces, dipole–dipole forces, hydrogen bonds and ion–dipole forces — identifying forces, ranking boiling points and explaining solubility — with full answers.
Ion–Dipole Forces and Why Salt Dissolves in Water
How ion–dipole forces let water pull ions out of a crystal: hydration shells, hydration enthalpy, the energy balance of dissolving, why charge and size matter, and why some salts don't dissolve.
Ionic Lattices: The Structure of Sodium Chloride
Inside a salt crystal: the rock-salt lattice of NaCl, coordination numbers, unit cells, how ion size sets the structure (CsCl, zinc blende, fluorite), and how X-rays revealed it.
Lewis Structures Practice: 20 Molecules and Ions with Answers
20 Lewis structure practice problems — from H₂O and CO₂ to SO₄²⁻, XeF₄ and ozone — with electron counts, full answers described step by step, formal charges and shapes.
London Dispersion Forces: The Weakest Force That Matters Most
What London dispersion forces are, how temporary dipoles form, why they grow with electron count, surface area and shape, and how they explain boiling points, geckos and why iodine is a solid.
How Lone Pairs Change Molecular Shape
What lone pairs are, why they take up more space than bonding pairs, and how they turn tetrahedral, trigonal bipyramidal and octahedral arrangements into bent, pyramidal, seesaw, T-shaped and square planar molecules.
How to Tell If a Molecule Is Polar
A four-step method to decide whether a molecule is polar: check bond polarity, find the shape, test for symmetry, and look for lone pairs — with 12 worked examples and quick shortcuts.
Naming Compounds with Transition Metals (Roman Numerals)
How to name compounds of metals with variable charges using Roman numerals (Stock system): working out the metal's charge, worked examples, old -ous/-ic names, and common pitfalls.
Naming Oxyanions: -ate, -ite, per- and hypo-
How to name oxyanions using -ate, -ite, per- and hypo-, the chlorine series, patterns across the periodic table, hydrogen-containing oxyanions, oxidation states and the matching acid names.
Resonance Structures: What They Are and How to Draw Them
Resonance explained: why one Lewis structure isn't enough, curly-arrow rules for drawing resonance forms, the hybrid, bond order, delocalisation energy, and examples from ozone to benzene.
Methane, Ammonia and Water: Same Electron Pairs, Different Shapes
CH₄, NH₃ and H₂O compared: four electron pairs each, but tetrahedral, pyramidal and bent shapes. Bond angles, polarity, hydrogen bonding, boiling points and acid–base behaviour side by side.
Sigma and Pi Bonds: What's the Difference?
Sigma vs pi bonds explained: head-on vs sideways orbital overlap, electron density, strength, rotation, which bonds contain which, and how pi bonds drive reactivity, colour and delocalisation.
Teaching Chemical Bonding: Models, Analogies and Pitfalls
A teaching guide for chemical bonding: a four-lesson sequence, physical models and analogies that work (and where they break), practical demos, misconceptions to pre-empt and graded questions.
Van der Waals Forces: What the Term Really Covers
What 'van der Waals forces' means — and why textbooks disagree — covering Keesom, Debye and London forces, van der Waals radii, the van der Waals gas equation and real-world examples.
VSEPR Practice Questions: Predict the Shape and Bond Angle
15 VSEPR practice questions on predicting molecular shapes and bond angles — from CH₄ and H₂O to ClF₃, XeF₂ and I₃⁻ — with a full answer key and the electron-pair reasoning.
Intermolecular Forces: London Dispersion, Dipole-Dipole and Hydrogen Bonds
The forces between molecules explained — London dispersion, dipole-dipole and hydrogen bonding — how to rank them, and how they control boiling points, solubility and viscosity.
Hydrogen Bonding Explained: Why Water Is So Strange
What a hydrogen bond is, why it only forms with nitrogen, oxygen and fluorine, and how it explains water's high boiling point, floating ice, DNA's double helix and protein shapes.
VSEPR Theory: How to Predict Molecular Shapes
How VSEPR theory predicts the 3D shape of molecules from electron pairs, the key shapes and bond angles, why lone pairs squeeze bonds, and worked examples from methane to water.
Metallic Bonding: The Sea of Electrons Explained
How metallic bonding works, the electron-sea model, and how it explains why metals conduct electricity and heat, are shiny, malleable and ductile — plus why alloys are harder.
Polar vs. Nonpolar Molecules: How to Tell the Difference
How electronegativity makes bonds polar, why molecular shape decides whether a whole molecule is polar, a quick method with examples, and why polarity controls what dissolves in what.
Chelation and the Chelate Effect Explained
Why ligands that grip a metal with several donor atoms form far more stable complexes: entropy, ring size, EDTA, and chelation in water softening, medicine and biology.
Coordination Chemistry Practice Questions (with Worked Answers)
14 advanced questions on complexes: oxidation states, IUPAC names, d-electron counts, high and low spin, spin-only magnetic moments and isomerism, with worked answers.
Crystal Field Theory: How Ligands Split the d Orbitals
Crystal field theory explained: why ligands split d orbitals, octahedral and tetrahedral patterns, Δo, CFSE, the spectrochemical series and colour.
Metal Crystal Structures: BCC, FCC and HCP Explained
Why most metals crystallise as body-centred cubic, face-centred cubic or hexagonal close-packed, how the three differ, and what that means for their properties.
Electron-Deficient Molecules: Boranes and Three-Centre Bonds
How diborane, B₂H₆, holds together with too few electrons: the electron count, 3-centre 2-electron B–H–B bridges, the MO picture, higher boranes and look-alikes.
Fajans' Rules: When Ionic Bonds Become Covalent
How cation size, charge and electron configuration distort anions, why AlCl₃ behaves covalently while AlF₃ is ionic, and the common mistakes with Fajans' rules.
Halogen Bonding: The Hydrogen Bond's Lesser-Known Cousin
How a σ-hole lets iodine, bromine and chlorine attract electron-rich atoms, why halogen bonds are so linear, and where they matter in crystals and drugs.
High-Spin vs Low-Spin Complexes: How to Tell Them Apart
High-spin vs low-spin complexes compared: Δo versus pairing energy, which d counts are affected, unpaired electrons, magnetism, size, colour and real examples.
Hypervalent Molecules: SF₆, PCl₅ and the Expanded Octet Debate
Do SF₆ and PCl₅ really have 12 and 10 electrons on the central atom? The d-orbital model, why it faded, and the modern 3-centre 4-electron and ionic picture.