Determining Spin in orbitals [ENDORSED]

[JakeSaum_1A]

In the lecture, when prof. Lavelle was finished writing down the shell letters and numbers, he started drawing arrows. I noticed how he drew 3 up arrows before complementing them with down arrows. Why did he do this and how did he know how many arrows to put? Thanks.

[Annika Tamaki 1E]

The number of arrows corresponds to the number of electrons. For example, if I had the configuration for Nitrogen, [He] 2s2 2p3, I would only put 3 arrows in the 2p level. I would only draw 3 uncomplemented arrows because it represents a more stable electron. You must fill all of the subshells first before adding the complementary electrons/arrows.

[Ria Nawathe 1C]

He drew 3 up-spin electrons first because according to Hund's Rule, electrons occupy empty orbitals in the same sub-shell before pairing up. As for why the up-spin electrons are drawn first, I think it just has to do with convention.

[Emmeline Phu 1G]

Hi! When drawing an electron configuration, the number of arrows corresponds to the number of electrons. The reason why he drew three up arrows before drawing down arrows is due to the Hund's rule in which due to e- repulsion, electrons in the same subshell occupy different orbitals with parallel spin (all up arrows) or in other words add parallel spins to different orbitals. Hope this helps! :)

[Nadya Higgins 3F]

In order for electrons to be more stable, they have to be further apart. They also must occupy the necessary amount of orbitals first corresponding to the number of electrons, shown by an up arrow (positive electron spin) before down arrows can be drawn. So you would draw all up arrows first in each occupied orbital of the subshell, and then draw any additional down arrows.

[Chem_Mod]

He drew 3 up-spin electrons first because according to Hund's Rule, electrons occupy empty orbitals in the same sub-shell before pairing up. As for why the up-spin electrons are drawn first, I think it just has to do with convention.

Good answer! Convention is is draw up spin electrons first, but you can draw all down spin first if you'd like.