The periodic table is organized by a) atomic mass. b) atomic size. c) atomic number. d) atomic periodicity.

The correct option is: c) atomic number

Explanation:

The periodic table is a table in which all the chemical elements are organized in the increasing order of atomic number (Z), which is unique for each chemical element.

The atomic number of a neutral element is equal to the number of protons present in the nucleus of the atom and the number of electrons in the atom.