If each orbital is indicated in an energy diagram as a square ( ), we can
show relative energies in a chart such as Figure 9. If this drawing represented a
ravine with the energy levels as ledges onto which stones could come to rest only
in numbers equal to the squares for orbitals, then pushing stones into the ravine
would cause the stones to lose their potential energy as they dropped to the lowest
potential level available to them. Much the same is true for electrons.
SUBLEVELS AND ELECTRON CONFIGURATION
Order of Filling and Notation
The sublevels do not fill up in numerical order, and the pattern of filling is shown
on the right side of the approximate relative energy levels chart (Figure 9). In the
first instance of failure to follow numerical order, the 4s fills before the 3d.
(Study Figure 9 carefully before going on.)