18-Column Periodic Table
The conventional form of the periodic table, organizing all 118 elements across 18 groups and 7 periods. It is a practical compression of the 32-column layout: the f-block (lanthanides and actinides, 14 columns wide) is detached from the main body and placed below, keeping the table compact enough for a standard page. The 32-column form is the truer representation — derived directly from the Aufbau principle and quantum shell filling (see § 6.8 — The Periodic Table Emerges).