Aufbau Principle [ENDORSED]

[Nikhita_Jaaswal_2H]

Hi,

I'm a little confused on what the Aufbau Principle and Hund's rule are referring to. Can someone please explain these concepts to me?

[Fengting Liang 1F]

Aufbau means that electrons fill the lowest possible energy levels first to create the most stable electron configurations (like 1s is always filled before 2s) and Hunds rule is that each orbital in each subshell is filled once before it's filled twice (and if they're filling them singly they all have the same spin, and then go back a second time with the different spin). It's like in monopoly when you own the whole set of a color, you have to put one house on every property before you can add another.

[Aleena_Sorf_2A]

According to the Aufbau Principle, electrons fill up orbitals with the lowest energy first before filling up the higher energy orbitals. For example, an electron configuration for Cl would be 1s^2, 2s^2, 2p^6, 3s^2 ,3p^5, because a 3p orbital has greater energy than a 2p orbital.

Hund's Rule states that every orbital is occupied by one electron before any other orbital has two electrons. Also, all electrons in one orbital, that are filled up singly, have the same spin.