CEM 181H-Lecture 11
The graph shows how the increasing
nuclear charge stabilizes (lowers the
energy of) the one-electron orbitals.
At a given Z, the order of orbital energies defines the loading order for the
electrons to first order.
2 hc RH = 4.3597 × 10 −18 J = 27.211eV
1 hartree = 2 Rydbergs =
Hartree-Fock/Single-Electron
Orbital Energies Describe the
Orbital-Filling Sequence to First
Order
CEM 181H-Lecture 11
2 of 9
1 of 9
You should:
1. understand the origin of the anomalies in electron configurations
which cause deviation from the filling orders predicted by 1-electron
orbitals.
2. know how to write electron configurations for neutral atoms and
ions, including those with anomalous electron configurations.
3. be able to explain and predict the periodic trends for atomic/ionic
radii, ionization energies, and electron affinities.
Learning Objectives-10/4
valence
Ar
3 of 9
CEM 181H-Lecture 11
4 of 9
Electron Density Contracts as the Nuclear Charge Increases
CEM 181H-Lecture 11
core
The valence electrons are shielded from the full effects of the nuclear positive charge
by the core electrons (the especially stable underlying noble-gas configuration).
Periodic Trends Arise from Shielding Effects
5 of 9
CEM 181H-Lecture 11
6 of 9
1. Write balanced equations for the processes associated with ionization energies and electron affinities.
2. Explain how atomic radii are determined.
In-Class Exercise
CEM 181H-Lecture 11
The degenerate p orbitals do not shield each other very much from the increasing
nuclear charge, so a significant contraction occurs as they are filled.
The Nuclear Charge is Not Well Screened by the p Orbitals
CEM 181H-Lecture 11
Periodic Trends in Electron Affinity
CEM 181H-Lecture 11
Periodic Trends in Ionization Energy/Potential
8 of 9
7 of 9
CEM 181H-Lecture 11
Periodic Trends in Atomic Radius
9 of 9