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.
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.
Due to violations of special relativity, this concept fails around atomic number 173.
{Aufbau} principle [accept {building}-{up principle} before it is mentioned]