Shared Electrons

[Ramneet Sandhu 3D]

During lecture, Dr. Lavelle said it would be better to write out p_x , p_y, etc. in order to be specific about whether the electrons are paired or not. How are you able to tell if electrons are paired so that you know to write it like this?

[Indy Bui 1l]

You have to refer to Hund's rule. Each orbital (for example Px,Py,Pz) must be filled with one electron before you pair electrons.

Take the element Nitrogen for example. Nitrogen's orbital notation at its ground state would be written as 1s1 2s2 2p3
In the P state, nitrogen has three unpaired electrons one for each axes. 1 electron in Px, 1 in Py, and 1 in Pz.

the 2p orbital for N would look like this ↾ ↾ ↾
2P __ __ __

Oxygen, the next element over would look like this ⇅ ↾ ↾
2P __ __ __

Oxygen has one more electron than Nitrogen, and that electron gets paired, because all the 3 P blocks have one electron in them already, but these must be full before electrons get paired.
You essentially know an electron is unpaired by understanding the electron configuration of the element you are evaluating

[MaggieHan1L]

It has to do with electron repulsions. The electrons make sure every orbital has one electron first because two electrons in the orbital has repulsions. At least that's what I remember from high school.

[gabbymaraziti]

This has to do with Hund's rule. Basically, if more than 1 orbital in a sub shell is available, you should add electrons with parallel spins to different orbitals before filling up a singular orbital. This configuration has slightly lower energy than that of a paired arrangement because it maximizes the attraction of the electrons to the nucleus and minimizes their repulsion by one another.

[eduardomorales5]

Hund's Rule tells us that because of the repulsion of electrons, they will first try to occupy different orbitals while having parallel spin, which has less energy than opposite spin electrons. Because there are 3 p orbitals, they will try to fill up each orbital first until they other electrons begin pairing.