What is the mass number of the isotope zinc-65?

• A. 30
• B. 95
• C. 35
• D. 65

Answer: (D)

Verified step by step guidance

1. Understand that the mass number of an isotope is the total number of protons and neutrons in its nucleus.
2. Identify the element zinc, which has an atomic number of 30. This means zinc has 30 protons.
3. Recognize that the isotope notation zinc-65 indicates the mass number is 65.
4. Recall that the mass number (A) is given by the sum: \(A = \text{number of protons} + \text{number of neutrons}\).
5. Since the isotope is zinc-65, the mass number is 65, which includes 30 protons and 35 neutrons.