Final answer:
The atomic number is always equal to the number of electrons.
Step-by-step explanation:
The atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element.
In all electrically neutral atoms, the number of electrons is the same as the number of protons. Thus, each element, at least when electrically neutral, has a characteristic number of electrons equal to its atomic number.
Therefore, the statement that is true is option 3) The atomic number is always equal to the number of electrons.