1.3.7—The electrons in boxes notation

In electron-box notation, each box represents one atomic orbital and each arrow represents one electron. Opposite arrow directions in one box show a pair with opposite spins.

Draw the required boxes for the sub-shell, place electrons in the supported energy order, and use one arrow in each equivalent orbital before pairing. The diagram therefore displays both the number of electrons and their orbital occupancy.

For a 2p⁴ sub-shell, draw three boxes as ↑↓, ↑, ↑. There are four arrows in total, one paired box and two unpaired electrons; the arrow directions make the spin information visible.

A box diagram and superscript notation represent the same configuration in different formats. Do not pair electrons while an equivalent orbital is empty, and do not interpret a box as a shell or a fixed planetary path.