Electrons tend to enter all shell orbitals before they fill any orbital with two opposite-spin electrons {Hund's rule} {Hund rule}. Hund's rule is true for small atoms, because it takes more energy to put two electrons into one orbital than into two different orbitals.
Physical Sciences>Physics>Matter>Atom>Orbital>Rules
5-Physics-Matter-Atom-Orbital-Rules
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Date Modified: 2022.0224