CU-101 · Atomic Structure & Periodicity
Where chemistry begins: the quantum atom, and why the periodic table has the shape it does.
None — this unit is the entry point to the canon.
Lectures
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Results in this unit
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.
Hess's law and enthalpy cycles
Enthalpy is a state function, so reaction enthalpies combine exactly as their equations do: every cycle closes and one formation table evaluates them all.
The Born-Haber cycle
Hess's law closes a six-leg cycle to extract the lattice enthalpy of an ionic solid, the one term no calorimeter can reach.