Building Up

[Marty Hockey]

What is the purpose of writing the electron structure of carbon as 1s^2 2s^2 2px^1 2py^1 as opposed to 1s^2 2s^2 2p^2?

[DarrenKim_1H]

According to Hund's rule, electrons repel each other in the same subshell which is why they must occupy different orbitals with parallel spin

[Jessica Castellanos]

This is actually due to Hund's rule to be more specific about where the electrons in the p orbital would be. Since there are two electrons in the p orbital in your example, they would not both be in the same orbital because that would increase the energy and the lowest energy possible would be with one electron in the 2px orbital and one in the 2py orbital with parallel spins, so writing it as 2px^1 2py^2 specifies the orbitals in which the electrons would be. Hope this helps!