Final answer:
The isotope name for a nucleus with 42 protons and 89 nucleons is 42Ca.
Step-by-step explanation:
The isotope name for a nucleus with 42 protons and 89 nucleons is 4220Ca. In this isotope, 42 represents the number of protons (atomic number) and 89 represents the number of nucleons (number of protons + number of neutrons). Calcium (Ca) is the element with atomic number 20, so it is used as the symbol.