The atomic number of an atom is the number of

a. electrons and neutrons
b. protons and neutrons
c. protons
d. neutrons

The atomic number of an atom is the number of protons (option C)

Explanation:

All atoms are composed of a central nucleus in which there are particles with positive electrical charge, the protons, around which other particles with negative electrical charge that are electrons move. Inside the nucleus it is also possible to find neutrons, which has no charge.

Each chemical element is characterized by the number of protons present in its nucleus, which is called the atomic number and is represented by the letter Z.

In the event that the atom is electrically neutral, that is to say that its charge is zero: the atomic number, in addition to indicating the number of protons, will indicate the number of electrons.

The atomic number is used to classify the elements within the periodic table of the elements, which where they are ordered by increasing order of atomic number.

Finally, the atomic number of an atom is the number of protons (option C)