Question

the atomic number tells you what?
number of protons
number of neutrons
number of electrons
both electrons and protons in an atom.

Explanation:

In chemistry (a subfield of Natural Science), the atomic number is defined as the number of protons in the nucleus of an atom. In a neutral atom, the number of electrons equals the number of protons, but the atomic number itself directly represents the number of protons. The number of neutrons is related to the mass number (mass number - atomic number = number of neutrons). So the atomic number tells the number of protons.

Answer:

A. number of protons