My question is, Hund's rule states that the electrons pair up only after each orbital in a sublevel is occupied by ______. I think its one electron, but the more I read I'm confused because it says about an electron with a spin cycle.
You are correct. Hund's rule states that an electron pairs when there is no other option available; i.e., when there is no orbital available with NO electron in it. Then it MUST pair with an electron that is already there. When that electron pairs, it does so with an electron of the opposite spin in one of the orbitals with an electron there. I hope this clears up any confusion you have.
To understand Hund's rule, we need to start with the basic principles of electron configuration.
Electrons in an atom occupy various energy levels and sublevels within those levels. Each sublevel can hold a specific number of electrons.
Hund's rule states that when filling degenerate (having the same energy) orbitals, such as those in the same sublevel, electrons will distribute themselves singly into available orbitals before pairing up. In other words, electrons will occupy separate orbitals of the same energy level (sublevel) first, and only then will they begin to pair up.
This rule helps us understand the arrangement of electrons in atomic orbitals based on their energy levels. It applies within a particular sublevel like p, d, or f.
For example, let's consider the p sublevel. The p sublevel consists of three separate p orbitals, each capable of holding two electrons. According to Hund's rule, when filling the p sublevel, each p orbital will be occupied by a single electron before any one of them pairs up.
In terms of your question, Hund's rule states that electrons pair up only after each orbital in a sublevel is occupied by one electron. So, your intuition is correct.
With regards to the confusion about "spin cycle," it is important to note that electrons have a property called spin, which can be either "spin up" or "spin down." This property helps to distinguish one electron from another and is represented by arrows pointing up or down in electron configuration diagrams. Hund's rule does not specifically refer to a "spin cycle," but rather to the distribution of electrons in orbitals within a sublevel.
In summary, Hund's rule states that electrons will distribute themselves singly into available orbitals before pairing up, with each orbital in a sublevel being occupied by one electron before pairing occurs.