Answer: periodic law.
Justification:
1) Although Mendeleev formulated the modern periodic table, ordering the elements according to their physical and chemical properties, there is not such law as Meneleev's Law.
2) The Pauli exclusion principle states that two electrons on an atom cannot have the same 4 quantum numbers, which drives to the fact that only two electrons can stay in the same orbital, each with opposite spin numbers.
3) Hund's rule states that the electrons with the same energy level will occupy the orbitals with the same spin before adding the electrons with the opposite spin.
4) Indeed the periodic law states that the elements are arranged in order of increasing atomic number, and there is a
periodic repetition of their physical and chemical properties.
