Electron Configuration Chart

An electron configuration is a map of where an atom keeps its electrons. It is the single most useful thing to know about an element, because everything else — the charge it forms, the bonds it makes, the group it sits in — follows from the arrangement of the outermost few.

How to read one

Take 1s² 2s² 2p⁶. The number is the shell (roughly, how far out), the letter is the shape of the orbital, and the superscript is how many electrons are in it. Each orbital type has a fixed capacity: s holds 2, p holds 6, d holds 10 and f holds 14.

The filling order

Electrons fill the lowest-energy orbital available, and energies overlap between shells — which is why 4s fills before 3d:

1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p → 7s → 5f → 6d → 7p

Every element

The shorthand column uses noble-gas notation; the expanded column spells out every orbital from 1s. Both describe the same atom.

Configurations that are predicted, not measured

For the superheavy elements past roentgenium, nobody has ever had enough atoms in one place long enough to measure a spectrum. Their configurations are calculated from relativistic quantum mechanics and are marked as predicted on their individual pages. They are good predictions — but they are predictions.