Question

An atomic model shows 19 protons, 20 neutrons, and 19 electrons. What is the mass number of the atom?(1 point)
39
39

19
19

20
20

58

Answer 1

The mass number of an atom is the sum of its protons and neutrons. In this case, the atom has 19 protons and 20 neutrons, so the mass number is 19 + 20 = 39.