5.3. Electron Arrangement in Atoms http://www.ck12.org
FIGURE 5.14
According to the Aufbau principle, all
lower energy orbitals must be filled before
electrons can be added to a higher energy
orbital. The principal energy levels are
color coded in this figure. Sublevels are
grouped together by column, and each
circle represents an orbital that is capable
of holding two electrons.FIGURE 5.15
The Aufbau principle is illustrated in the
diagram by following each red arrow in
order from top to bottom: 1s, 2s, 2p, 3s,
etc.