Aufbau Principle

The Aufbau principle (from the German Aufbau meaning "building up, construction": also Aufbau rule or building-up principle) is used to determine the electron configuration of an atom, molecule or ion. The principle postulates a hypothetical process in which an atom is "built up" by progressively adding electrons. As they are added, they assume their most stable conditions (electron orbitals) with respect to the nucleus and those electrons already there.
According to the principle, electrons fill orbitals starting at the lowest available (possible) energy levels before filling higher levels (e.g. 1s before 2s). The number of electrons that can occupy each orbital is limited by the Pauli exclusion principle. If multiple orbitals of the same energy are available, Hund's rule states that unoccupied orbitals will be filled before occupied orbitals are reused (by electrons having different spins).
A version of the Aufbau principle can also be used to predict the configuration of protons and neutrons in an atomic nucleus.
== Tossup Questions ==
# Due to violations of special relativity, this concept fails around atomic number 173. In 1990, the IUPAC changed the numbering of groups to better reflect this concept, which explains the increased shielding of nuclear charge across a period. Madelung's (mah-DEH-loongz) rule determines order in this concept, while copper and chromium are no- table exceptions to it, since both lack full s orbitals in their electron configurations. Forcing three-d orbitals to be filled after four-s orbitals, name this principle whose name comes from the German for "building up", and which requires electrons to enter atomic orbitals in a pattern that minimizes the total potential energy.
# The Madelung rule can generally describe the same behavior that this predicts. A version of it can be used to predict the configuration of protons and neutrons in various atomic nuclei. The periodicity of ionization energy in relation to atomic number is a result of shielding from previously filled orbitals and a consequence of it. It is the result of the combination of Hund's Rules and the Pauli Exclusion Principle, and it is used to determine electron configurations. For 10 points, name this principle that governs orbital designations which is German for "to build up."