Question

Which of the following isotopes is likely to be most stable ?

• A. ${}_{30}^{71}Zn$
• B. ${}_{30}^{66}Zn$
• C. ${}_{20}^{40}Ca$
• D. None of these

Answer 1

The correct option is C ${}_{20}^{40}Ca$

The nucleus of each atom contains protons and neutrons. While the number of proton defines the element and the number of neutrons defines the isotope of the element. Radioactive isotopes are unstable and decays into other elements.