Browse the full table laid out by group and period, use the search box to jump to an element by name, symbol or atomic number, and click any tile to open its detail panel with mass, category, configuration and state.
The standard atomic weights published by IUPAC, given to five significant figures. For elements with no stable isotope, such as technetium and everything beyond bismuth, the value shown is the mass number of the most stable or best-characterised isotope, which is the usual convention.
Configurations follow the Madelung (aufbau) filling order, with the well-known experimental exceptions applied individually — chromium, copper, niobium, molybdenum, palladium, silver, platinum, gold, lanthanum, cerium, gadolinium and the early actinides all show their measured configurations rather than the naive prediction.
The f-block is conventionally printed below the main table so the chart fits a page. Lanthanum to lutetium all sit in period 6 and actinium to lawrencium in period 7, between groups 2 and 3, and clicking any of them shows its true period.