Barrons SAT Subject Test Chemistry, 13th Edition

Table 3. Electron Configuration of the Elements

Note: Follow order of the atomic numbers to ascertain the order of filling.

By following the atomic numbers in numerical order in Table 3 you can plot
the order of filling of the orbitals for every element shown.
A simplified method of showing the order in which the orbitals are filled is
to use the following diagram. It works for all the naturally occurring elements
through lanthanum, atomic number 88.

TIP

This is a simple way to remember the order of filling orbitals.