Question

the \atomic number\ of an atom is determined by the number of ______ it has.
neutrons
protons + neutrons
electrons
protons
protons + electrons

Explanation:

The atomic number of an atom is defined as the number of protons in its nucleus. Neutrons contribute to the mass - number (protons + neutrons), electrons are involved in chemical bonding and do not determine the atomic number.

Answer:

D. protons