3 1. The observed regularities in the properties of
the elements are periodic functions of their
(1) atomic numbers
(2) mass numbers
(3) oxidation states
(4) nonvalence electrons

The observed regularities in the properties of  the elements are periodic functions of their atomic numbers.

Modern periodic law states that "Properties of elements are a periodic function of their atomic number not by their atomic mass". Modern periodic law was proposed by Henry Moseley in 1913. Physical and chemical properties of elements depend on the number of electrons and their arrangement.

Thus properties of elements are periodic function of their atomic numbers and not atomic masses. If the properties of an element depend on number of proton and neutron then the properties are periodic function of their atomic mass so we can conclude that the observed regularities in the properties of  the elements are periodic functions of their  atomic numbers.

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(1) atomic numbers

Explanation:

The observed regularities in the properties of the elements on the periodic table are periodic functions of their atomic numbers.

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