This symbol shows that chlorine has 35 particles in the nucleus ... number. Key fact: isotopes are forms of an element that have the same number of protons but different numbers of neutrons.

Dr. Aston has recently announced the discovery that chlorine consists of a mixture of at least two isotopes having atomic weights 35 and 37. It appears that there is here a possibility of ...

The different types of chlorine are called isotopes of chlorine ... and different chemical symbol - they are not the same element. If the number of protons changes, then it is a different element.