The distribution of an atom's electrons among its orbitals, such as 1s2 2s2 2p6 for neon.
Practise Atomic Structure & Periodicity All Atomic Structure & Periodicity topics
An electron configuration lists the distribution of an atom's electrons among its subshells, with the number of electrons written as a superscript after each subshell label. For example, neon is 1s2 2s2 2p6. The configuration determines the valence electrons, magnetism and periodic trends of the element. When writing configurations for ions, electrons are removed first from the highest n shell, so 4s electrons leave before 3d electrons. Configurations are the foundation of modern bonding theory.
Key ideas: Write the occupied subshells with superscripts adding to Z, such as Cl: 1s2 2s2 2p6 3s2 3p5. For ions subtract electrons from the highest n first (and from p before s in the same shell), e.g. Fe3+ is [Ar] 3d5. Orbital diagrams add spin detail. Use it to find valence electrons, unpaired electrons, and magnetic behavior.
Common mistakes and connections: Students forget that cations lose the highest n electrons, not those filled last, and for anions they add to the next available orbital. The totals must equal electron count rather than Z for ions. It predicts periodic trends, oxidation states and bonding.
Iron has 26 electrons in shells of 2, 8, 14 and 2, corresponding to 1s2 2s2 2p6 3s2 3p6 3d6 4s2. The interactive lesson shows this as a live animation or chart.
Iron is [Ar] 3d6 4s2 as a neutral atom, but Fe3+ is [Ar] 3d5.
The distribution of an atom's electrons among its orbitals, such as 1s2 2s2 2p6 for neon.
Electron Configuration is a beginner topic in Atomic Structure & Periodicity. It needs no earlier chemistry lessons and is a good starting point.
Study these earlier topics in Atomic Structure & Periodicity first: Pauli Exclusion Principle, Hund's Rule, Madelung Rule.
The next topics in Atomic Structure & Periodicity are Noble Gas Shorthand and Exceptional Configurations of Cr and Cu.
Yes. The interactive lesson includes a self-check question on Electron Configuration, and the Atomic Structure & Periodicity quiz draws on every topic in this area.
Electron Configuration is topic 65 of 115 in Atomic Structure & Periodicity.