Chlorine doesn't have a single, fixed number of neutrons. Here's why:

* Isotopes: Chlorine has two main isotopes, which are atoms of the same element with different numbers of neutrons.

* Chlorine-35: Has 18 neutrons (35 - 17 = 18)

* Chlorine-37: Has 20 neutrons (37 - 17 = 20)

* Atomic Number: Chlorine's atomic number is 17, meaning it always has 17 protons. The number of neutrons can vary.

* Average Atomic Mass: The average atomic mass of chlorine is 35.45, which reflects the abundance of each isotope.

So, to answer your question: Chlorine has either 18 or 20 neutrons, depending on the specific isotope.