Isotope A contains 56 protons and 80 neutrons. Isotope B contains 55 protons and 82 neutrons. Isotope C contains 57 protons and 80 neutrons. Isotope D contains 56 protons and 74 neutrons. Which are isotopes of the same element?

Answer 1

Isotopes of the same element have the same number of protons, but different numbers of neutrons.

• Isotope A has 56 protons.
• Isotope B has 55 protons.
• Isotope C has 57 protons.
• Isotope D has 56 protons.

From this information:

• Isotope A (56 protons, 80 neutrons) and Isotope D (56 protons, 74 neutrons) are isotopes of the same element, as they both have 56 protons.
• Isotope B (55 protons) and Isotope C (57 protons) are not isotopes of A or D, since they have different numbers of protons.

Therefore, Isotopes A and D are the isotopes of the same element.