Atomic Structure: From Bohr's Orbit to the Quantum Orbital

In the paper

Unit 1 carries 17 of the 50 chemistry marks; with fourteen chapters sharing them, this one averages a little over one (MEC publishes weights by unit, not by chapter). It is one of the two heavy chapters in Physical chemistry, because it is the only place in the syllabus where three clean formulae can be plugged with numbers, and because every configuration in Periodicity and Chemical bonding is written with the rules set out here.

The MEC scope line runs: Rutherford's and Bohr's atomic models; spectrum of the hydrogen atom; de Broglie's wave equation; Heisenberg's uncertainty principle; orbitals and quantum numbers; Aufbau principle, Pauli's exclusion principle and Hund's rule; electronic configuration. The headings below are its points, in MEC's order.

Three ways it comes: recall (the quantum number ranges, the series that lies in the visible, a defect of Rutherford's model); understanding (why Bohr's model fails for helium, why 4s fills before 3d, why Cr is 3d⁵4s¹); application (a radius or energy at a given n, a Rydberg wavelength, a de Broglie wavelength, an uncertainty limit).