The document discusses electron configuration and the rules that govern how electrons fill atomic orbitals: 1) The Pauli Exclusion Principle states that each orbital can hold two electrons with opposite spins. 2) The Aufbau Principle states that electrons fill the lowest energy orbitals first, following the "lazy tenant rule." 3) Hund's Rule states that within a sublevel, one electron will occupy each orbital before pairing electrons, following the "empty bus seat rule."