How would you classify the fact that all available orbitals must recieve one electron each before receiving a second electron? in other words, which principle states that electrons will occupy equal-energy orbitals so that a maximum number of unpaired electrons results?

The best answer to the question: In other words, which principle states that electrons will occupy equal-energy orbitals so that a maximum number of unpaired electrons results? Would be: Hund´s Rule.

Explanation:

We must first remember that electrons are negatively charged, and therefore, they will tend to reject each other when they get close together. As such, electrons tend to seek such separation by initially filling up orbitals that have not yet been occupied by other electrons, starting from those at the sublevels and moving to the higher energy levels, and later they might start pairing up. The one rule that states this exactly, and explains the way that electrons will first fill up orbitals singly, and then later on start the pairing process, is known as Hund´s rule.

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