Handful resources of Aufbau diagrams are available here. The diagrams are based on the Aufbau principle which states that, hypothetically, eelctrons orbiting one or more atoms fill the lowest available energy levels before filling higher levels (e.g., 1s before 2s). In this way, the electrons of an atom, molecule, or ion harmonize into the most stable electron configuration possible. Click on the following diagram to learn more.
Shown on the diagrams, there are many possible ways to use the aufbau principle, incluing to figure the fill order of an atom’s orbitals is to try and memorize the order by brute force: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 8s. Fortunately, there is a much simpler method to get this order. First, write a column of ‘s’ orbitals from 1 to 8. Second, write a second column for the ‘p’ orbitals starting at n=2. (1p is not an orbital combination allowed by quantum mechanics) Third, write a column for the ‘d’ orbitals starting at n=3. Fourth, write a final column for 4f and 5f. There are no elements that will need a 6f or 7f shell to fill. Finally, read the chart by running the diagonals starting from 1s. Take a look at the following diagrams.
An Aufbau diagram uses arrows to represent electrons. When there are two electrons in an orbital, the electrons are called an electron pair. Electron pairs are shown with arrows pointing in opposite directions. An arrow pointing up denotes an electron spinning one way and an arrow pointing downwards denotes an electron spinning the other way. If the orbital only has one electron, this electron is called an unpaired electron.
Orbitals are like “rooms” within which electrons “reside”. The s subshell has one s-orbital. The p subshell has three p-orbitals. Get these diagrams as your teaching or learning resources in studying about the Aufbau principle. More diagrams are available in the other posts in this site!