Question

why chlorine occurs in two isotopic forms​

Answer 1

Answer:

Chlorine-35 and chlorine-37 are both isotopes of the element chlorine. The number after the name 'chlorine' is called the mass number. The mass number is a tally of the number of protons and the number of neutrons in an atom's nucleus.

Answer 2

Answer:

Because each isotope has different number of neutrons

I really don't know why but this is the definition taught to me that isotopes are the elements having the same atomic number but different mass number