Question

the periodic table consists of elements following a repeating pattern of
a. outermost electrons.
b. nuclei.
c. hydrogen ions.
d. excess neutrons.

Explanation:

The periodic table is organized by periodic trends based on electron configuration. Elements in the same group (column) have the same number of outermost (valence) electrons, leading to similar chemical properties. This repeating pattern of valence electrons defines the table's structure. Nuclei, hydrogen ions, and excess neutrons do not follow the periodic repeating pattern that organizes the table.

Answer:

A. outermost electrons.