Press any element and watch the subshells fill in order. The model uses the measured ground state, so chromium, copper and the other oddities come out right.
Faded cells hold fewer electrons than the element you picked. The bright cell is your element.
| Simple order | — |
| Measured | — |
A cation loses electrons from the shell with the largest n. An anion adds them to the next open subshell. Only the anions that real chemistry makes are offered here, so most metals show cations alone.
Add up every superscript. The total has to match the electron count exactly. If it does not, a subshell was filled past its limit.