The Periodic Table and the Electron: Although electronic configurations are traditionally invoked to explain the periodic system, their explanatory power remains only approximate ...

We now have enough knowledge to build the periodic table from scratch. The electron configuration for hydrogen can be written as 1s 1, where: 1 = The principal quantum number (n) or shell.

The Royal Society of Chemistry instead puts lanthanum and actinium in these upper boxes, prioritizing outer electron configurations and sticking lutetium and lawrencium at the end of the f-block.