Chemistry · Atomic structure. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
De Broglie proposed that a moving particle, such as an electron, also behaves as a wave. Heisenberg showed that we cannot know both the exact position and the exact momentum of an electron at the same time. So we cannot draw a fixed path for it as Bohr did. We speak instead of an orbital: a region around the nucleus where the probability of finding the electron is greatest.
Four quantum numbers describe each electron: its shell, its subshell, the orientation of its orbital and its spin.
The electronic configuration shows how the electrons of an atom are spread over its orbitals. Three rules decide it: the Aufbau principle with the (n + l) rule, the Pauli exclusion principle and Hund's rule.
Students confuse the number of orbitals with the number of electrons: a d subshell has 5 orbitals but holds 10 electrons. Also remember that l can never equal n; its largest value is n − 1.
Answer: Cu: [Ar] 3d10 4s1.
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