Which statement best describes how electrons fill orbitals in the periodic table?

As you move from left to right across a period, electrons are added to orbitals in a sequence that generally follows increasing orbital energy. Thus, choice A, “Electrons fill orbitals in order of their increasing energy from left to right,” is the best description. The top-to-bottom statements describe moving down a group, not the usual order of orbital filling across the periodic table.

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