An isotope has an atomic number of 17 and a mass number of 36. Which of the following gives the correct number of neutrons and protons in an atom of…

Explanation

Every atom has three types of subatomic particles: protons, neutrons, and electrons. The atomic number and mass number help us figure out how many of each particle an atom has.

The atomic number tells us the number of protons in an atom. It is the smaller number and defines what element the atom is. Here, the atomic number is 17, so this atom has 17 protons. (This is chlorine, by the way.)

The mass number is the total number of protons and neutrons added together. It does not include electrons because electrons have very tiny mass. Here, the mass number is 36.

To find the number of neutrons, subtract the atomic number from the mass number:
Neutrons = Mass number − Atomic number
Neutrons = 36 − 17 = 19

So this isotope has 17 protons and 19 neutrons. The common isotope of chlorine has a mass number of 35 (18 neutrons), but this is a heavier isotope with one extra neutron.