the sum of the protons and neutrons in an atom or isotope is called select the best option. atomic number…
the sum of the protons and neutrons in an atom or isotope is called select the best option. atomic number mass number valence electrons
Answer
Brief Explanations:
The atomic number is the number of protons. Valence electrons are the out - most electrons. The mass number is defined as the sum of protons and neutrons in an atom or isotope.
Answer:
B. mass number