structure
66 results carry this thread across the degree.
The Bohr model of hydrogen
Quantised electron orbits give energy levels E_n = -13.6/n^2 eV.
The Rydberg formula
Every hydrogen spectral line from a single expression in 1/n^2.
Quantum numbers and atomic orbitals
Four quantum numbers label every electron in an atom.
The building-up principle
Aufbau order, Hund's rule and the Pauli principle fix ground-state configurations.
Periodic trends
Effective nuclear charge explains atomic size and ionisation energy across the table.
Ionisation and the photoelectric effect
Electrons are ejected only above a threshold photon energy.
The mole and Avogadro's constant
Linking the mass of a sample to the number of particles.
Empirical and molecular formulae
From composition by mass to a chemical formula.
The limiting reagent
Which reactant caps the theoretical yield.
Gas stoichiometry
Equal volumes of gas contain equal numbers of molecules.
Concentration and dilution
Molarity and the c1V1 = c2V2 relation.
The ideal gas law
PV = nRT, assembled from the empirical gas laws.
Kinetic theory of gases
Pressure as the rate of molecular momentum transfer to the walls.
The distribution of molecular speeds
Temperature sets the spread of molecular speeds.
The van der Waals equation
Real gases corrected for molecular size and attraction.
Graham's law of effusion
Effusion rate varies inversely with the square root of molar mass.
Functional groups and nomenclature
The reactive handles that organise organic chemistry.
Structural and stereoisomerism
One formula, many distinct molecules.
Chirality and optical activity
Molecular handedness and its measurable signature.
Conformational analysis
The energy landscape of rotation about single bonds.
Degree of unsaturation
Counting rings and multiple bonds from a molecular formula.
SN1 and SN2 substitution
Two contrasting routes for nucleophilic substitution.
E1 and E2 elimination
Forming alkenes by loss of a leaving group.
Electrophilic addition and Markovnikov's rule
Regiochemistry of addition to alkenes.
Electrophilic aromatic substitution
Directing and activating effects on the benzene ring.
Nucleophilic addition to carbonyls
The reactivity of the carbon-oxygen double bond.
Reaction energy profiles
Intermediates, transition states and the rate-determining step.
Crystal field theory
d-orbital splitting in an octahedral ligand field.
Colour and the spectrochemical series
Why coordination complexes are coloured.
The chelate effect
Entropy stabilises multidentate complexes.
Isomerism in complexes
Geometric and optical isomers of coordination compounds.
Coordination number and geometry
Predicting the shapes of metal complexes.
The Beer-Lambert law
Absorbance proportional to concentration and path length.
Rotational spectroscopy
Bond lengths from the rigid-rotor microwave spectrum.
Vibrational (IR) spectroscopy
The harmonic oscillator and vibrational selection rules.
NMR and the chemical shift
Reporting the nuclear environment through resonance.
UV-visible spectroscopy
Electronic transitions and chromophores.
Mass spectrometry
Molecular mass and structure from fragmentation.
Crystal lattices and the unit cell
Describing periodic solids from a repeating motif.
Bragg's law
Diffraction reveals the spacing of crystal planes.
Close packing and packing efficiency
How hard spheres fill space.
Band theory of solids
Conductors, insulators and semiconductors from overlapping orbitals.
The Born-Lande equation
Lattice energy from electrostatics and repulsion.
Retrosynthetic analysis
Planning a synthesis by working backwards from the target.
The Diels-Alder reaction
A concerted, stereospecific cycloaddition.
Protecting group strategy
Masking reactivity to control a synthesis.
Stereoselective synthesis
Controlling which stereoisomer is formed.
Transition-metal cross-coupling
Forming carbon-carbon bonds catalytically.
Periodic trends across the p-block
Down-group and across-period patterns of behaviour.
Hard and soft acids and bases
Predicting the stability of adducts and complexes.
Frost diagrams
Oxidation-state stability seen at a glance.
Structures of main-group compounds
Applying VSEPR across the elements.
Trends in oxide acidity
From basic to acidic across a period.
Gravimetric analysis
Quantifying an analyte by the mass of a precipitate.
Chromatographic separation
Separation by differential partition between phases.
Uncertainty propagation
Combining measurement errors through a calculation.
Calibration and standard addition
Quantifying a signal against known standards.
Michaelis-Menten kinetics
Enzyme rate as a function of substrate concentration.
Enzyme inhibition
Competitive and non-competitive kinetic signatures.
Protein folding thermodynamics
The free-energy balance of the native state.
DNA base pairing
Hydrogen bonding and the double helix.
ATP and free-energy coupling
Driving unfavourable reactions with a favourable one.
Degree of polymerisation
Chain length and the molar-mass distribution.
Step- and chain-growth polymerisation
Two mechanisms for building macromolecules.
The glass transition
The freezing of an amorphous polymer.
Flory-Huggins theory
The thermodynamics of polymer solutions.