Question About Electron Configuration [ENDORSED]

[michaelcrisera]

In Dr. Lavelle's lecture on Friday, he mentioned the electron configuration of Carbon to be 1s2 2s2 2px1 2py1. I was wondering if somebody could clarify/explain the reason that the two electrons in the 2p orbital are divided into 2px and 2py. I believe it has something to do with the quantum numbers, but I could be wrong.

[Meg Yuan 1G]

The splitting up of electrons into 2px and 2py is due to Hund’s Rule, which states that each orbital in a subshell will be occupied by a single electron before pairing up of electrons within each orbital occurs. Think: parallel spin first, then spin paired electrons when filling the p-orbitals.

[Shivani Sakthi 1l]

Hello! To begin, the x1 and y1 subscript present in the carbon electron configuration denotes the ml quantum numbers. These are also known as the magnetic quantum numbers which label the different orientations of orbitals within different subshells. For example, in the case of carbon, the principal energy level is n=2. Knowing this, we can note that the angular momentum quantum numbers, or l, are 0 and 1. Therefore, the s and p subshells can be filled. Finally, we know that within the p subshell, there are 3 separate orbitals electrons can occupy. The formula 2(L)+1 tells us how many orbitals are present within a subshell, or the magnetic quantum number. The possible values of magnetic quantum numbers range from -L to L. So the possible ml values are (-1, 0, 1), which can be denoted as (px, py, and pz). Now we know the possible orbitals electrons can occupy. Finally, Hund's rule states that every orbital in a subshell must be occupied by a single electron before it is paired. Therefore, a single electron must be placed in each orbital in a parallel manner before pairing the electrons with those of opposite spins. In terms of carbon, after the Helium Core, the 2s orbital is filled. This leaves 2 electrons to occupy the P orbitals. So one electron will be placed in the 2px orbital, and the next electron will be placed in the 2py orbital with a parallel spin. Hope this helped!