Final answer:
Element Z, which exists as 35/17 Z and 37/17 Z, exhibits the phenomenon of isotopes, atoms of the same element with different neutron numbers but the same proton number.
Step-by-step explanation:
The phenomenon exhibited by element Z, which exists as 35/17 Z and 37/17 Z, is called isotopes. Isotopes are atoms of the same element (same atomic number, Z) that have different numbers of neutrons and therefore different mass numbers (A). In the given example, both isotopes have the same number of protons (17), but they differ in their mass numbers, with one isotope having a mass number of 35 and the other a mass number of 37. This difference in mass number is due to a difference in the number of neutrons in the nucleus. Isotopes can have different physical properties, but they have the same chemical properties because they have the same number of protons and electrons.