Question

for an atom (which is neutral), which of these must be true? the number of electrons is equal to the number of neutrons the atomic number is equal to the mass number the number of protons is equal to the number of electrons the number of protons is equal to the number of neutrons

Explanation:

In a neutral atom, protons (positively - charged) and electrons (negatively - charged) balance each other. So, the number of protons must equal the number of electrons. Atomic number is number of protons, mass number is sum of protons and neutrons, and there is no fixed equality between electrons and neutrons or protons and neutrons in a neutral atom.

Answer:

The number of protons is equal to the number of electrons