FIELD NOTES / 04
Electrons & chemical behaviour
A guide to the notation inside an atom.
Electron configurations describe how electrons occupy atomic orbitals. The labels s, p, d and f refer to different subshells.
A bracketed noble-gas symbol abbreviates the inner-electron configuration. For example, [He] in carbon represents the same inner configuration as helium.
Outer electrons strongly influence bonding. Electronegativity describes an atom’s tendency to attract electrons in a bond; the Pauling scale is dimensionless.
Practice: count the electrons
Read magnesium’s configuration as 1s² 2s² 2p⁶ 3s². Add the superscripts: 2 + 2 + 6 + 2 = 12. This matches the atomic number for a neutral atom. The letters identify subshells; the superscripts count electrons, not protons
Check your understanding
In the shortened form [Ne]3s², are there only two electrons?
Show the explanation
No. [Ne] stands for ten electrons in the neon configuration. Adding the two 3s electrons gives twelve. A configuration describes electron occupancy, not a picture of circular planetary paths
Scientific reference: OpenStax Chemistry 2e