Bonding & Structure is a core part of IB Chemistry. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Ionic bondingElectrostatic attraction between oppositely charged ions in a giant lattice.
Covalent bondingA shared pair of electrons between non-metal atoms.
Metallic bondingAttraction between metal ions and delocalised electrons.
Simple molecularSmall molecules with weak intermolecular forces; low melting points.
Giant structuresGiant ionic, covalent or metallic lattices with high melting points.
Intermolecular forcesWeak forces between molecules that affect melting and boiling points.
Ionic bondElectrostatic attraction between cation and anion formed by electron transfer; large electronegativity difference.
Covalent bondShared pair of electrons between non-metal atoms; Lewis 1916 dot structures.
Metallic bondLattice of cations in sea of delocalised electrons; explains conductivity and malleability.
VSEPR theoryElectron pairs minimise repulsion; predicts molecular shape (Gillespie & Nyholm 1957).
Hydrogen bondIntermolecular force when H bonded to N, O, F interacts with lone pair on N, O, F of another molecule.
ResonanceDelocalised electrons in structures like benzene or carbonate; actual structure is hybrid of canonical forms.
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
What does an NMR chemical shift (δ, in ppm) actually measure?✗ Chemical shift is the absolute resonance frequency of the nucleus in Hz. ✓ The position of a peak RELATIVE to TMS (tetramethylsilane, δ = 0), normalised by the spectrometer frequency.
What kind of bond forms between a ligand and a central metal ion in a complex?✗ The ligand forms an ionic bond with the metal because the metal is positively charged. ✓ A dative (coordinate) covalent bond — the ligand donates a lone pair into an empty orbital on the metal.
If a complex ion has a coordination number of 4, what shape does it have?✗ A coordination number of 4 always means tetrahedral, because that gives the maximum bond-angle separation. ✓ It can be either tetrahedral OR square planar — the shape depends on the metal and ligands (e.g. [Pt(NH3)4]2+ is square planar; [CuCl4]2- is tetrahedral).
What does the M+ peak in a mass spectrum represent?✗ The M+ peak shows the mass of the largest fragment after the molecule breaks apart. ✓ The molecular ion — formed when a single electron is removed from the whole molecule, giving the relative molecular mass.
What state are the ions in when defining lattice enthalpy of formation?✗ The ions are in aqueous solution before forming the lattice. ✓ Gaseous ions — lattice enthalpy is the energy change when one mole of solid ionic compound forms from its constituent ions in the GAS phase.
Practise Bonding & Structure — free games
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