The atomic number of an atom is determined by the number of what it has

Question

the atomic number of an atom is determined by the number of what

Answer 1

Atomic number is the number of protons an element has. If it had more or fewer protons, it would be a different element. Atomic mass is different in that it measures protons and neutrons and so various isotopes of elements that have various numbers of neutrons will change the atomic mass of an element.