6.2. Electron Configuration and the Periodic Table http://www.ck12.org
FIGURE 6.3
This periodic table shows the outer electron configurations of the elements.occurs. In other words, the 3d sublevels fills during the fourth period. The f sublevel is always two levels behind.
The 4f sublevel belongs to the sixth period.
Numbering the Periodic Groups
The vertical columns, or groups, of the periodic table contain elements that exhibit similar properties. Two different
ways of numbering the groups are commonly in use. The currently preferred convention is to number each column
of the periodic table from 1-18. Group 1 includes hydrogen, lithium and sodium, and group 18 includes helium,
neon, argon, and krypton. An older method is to skip the d and f blocks and utilize Roman numerals from IA to
VIIIA. The letter A differentiates these groups from the d block groups, which are numbered using the letter B (from
IB to VIIIB). For example, the element carbon could be described as being part of group 14 or group IVA, while
scandium is in group 3 or group IIIB.