Hund's Rule

[Kayley Steele 3D]

Could someone further explain what Dr. Lavelle meant in Lecture on Friday when he was going over Hund's Rule and how the electrons in the same subshells occupy different orbitals with parallel spin?

[AlexandriaHunt2J]

Hey! Hund's rule essentially states that when electrons occupy orbitals, orbitals of the same subshell are each occupied by 1 electron (all with the same spin) before 2 electrons can occupy one orbital. For example, for the 2p shell, there are 3 orbitals total: 2px, 2py, and 2pz. When electrons are filling these orbitals, first, one electron is distributed into each orbital individually before electrons are doubled up into each orbital. This is to minimize electron-electron repulsions.

[Robert Nguyen 14B-3E]

So, we can look at the 3 2p orbitals for an example. When filling up this level, according to Hund's rule, only one electron will go into each orbital until they are all filled, after which further electrons will pair with previously filled orbitals. This happens because electrons close together would repel each other, so it would take less energy to move to another orbital than to deal with the repulsion. Each single electron from the initial filling would also have the same spin (either spin up or spin down, depending on whichever one the first orbital is). I believe this occurs because having the same orbits means they interact with each other less (ex. two planets going clockwise wouldn't meet, but one going counterclockwise would have moments it goes near the other one. With electrons, this would cause repulsion, and therefore more energy usage, which is less favorable).

[Jessica Ghiuzelian 1H]

Hund's Rule states that because of electron repulsion, electrons in the same subshell must occupy different orbitals with the same spin. For example, if you try to stick magnets together with their positive sides towards each other, the magnets will begin to repel each other. It would be the same case with the electrons, so like-spin electrons must fill all empty orbitals first before they can share an orbital with an electron with opposite spin.

[205678283]

When I first learned about Hund's rule, my teacher drew it out in a diagram that helped me so maybe it will help you too! If you think about the sub shells/orbitals as little lines, such as:
2p _ _ _
then this will help you visualize! Okay, now remember that each orbital (little line) can have two electrons (That's from the Pauli exclusion principle). So when you fill out these little lines with arrows representing electrons, you have to fill out each line with one arrow/electron, before you can pair them to have two arrows/electron per line. So if we wanted to fill the 2p shell here with 3 electrons it would be:
2p _/ _/ _/ (imagine the dash is a spin up arrow haha!)
but if we had 5 electrons for this sub shell, then we could go pack and now add the pairs:
2p _// _// _/ (two electrons on first line(one spin up one spin down), two on second(one spin up one spin down), and one on third(one spin up))

hope that helps!

[005683006]

It states that orbitals tend to be all singly filled out first before it is doubly filled out.

[Kimberly_martinez2I]

Hi!. So Hund's rule states that all the orbitals are occupied singly before electrons double up.

[Kirsten Yu 2K]

Hund’s rule: due to e- repulsion, e- in the same subshell occupy different orbitals with parallel spin (lowest energy)

[Alekhya_Pantula_2E]

Essentially in electron configuration when the electrons are being distributed, each orbital must be occupied by one electron before it is occupied by 2 electrons as that results in a more stable atom. Then when the electrons are single and in each orbital, they all spin the same way, as electrons can spin up or down. The time when the spins would be different is when 2 electrons occupy one orbital, then they spin in opposite directions.

[Jiayin Yola Yan 1G]

Hund's rule basically states that electrons will try to be distributed in different orbits first (that is, parallel), rather than stay in the same orbit and be repelled by each other.