Suppose we have three hypothetical atomic nuclei: A, B, and C. Nucleus A has 7 protons and 7 neutrons. Nucleus B has 5 protons and 7 neutrons. Nucleus C has 7 protons and 5 neutrons. Which of the two nuclei are isotopes of the same element

Nucleus A with 7 protons and 7 neutrons and Nucleus C with 7 protons and 5 neutrons are isotopes of the same elements

Explanation:

Isotopes are elements that have the same atomic structure but different molecular structure. An atom that has the same atomic number but different mass number are known to be isotopes.

The proton of an atom is the same as its atomic number while the sum of the proton and neutron is equal to its mass number.

According to the question, nuclei that has the same number of proton are isotopes of the same element. Therefore nuclei A and C with 7 protons each are isotopes of the same element since they have the same atomic number i. e number of proton = atomic number.

Their atomic masses of nuclei A and C are 14 and 12 respectively