The element rhenium (Re) exists as two stable isotopes and 18 unstable isotopes. Rhenium-185 has in its nucleus

a. 75 protons, 75 neutrons

b. 75 protons, 130 neutrons

c. 130 protons, 75 neutrons

d. 75 protons, 110 neutrons

e. not enough information

d. 75 protons, 110 neutrons

Explanation:

In an isotope, the number next to the number of the atom is the mass number (Protons + neutrons). Rhenium has as atomic number 75, that means Rhenium has 75 protons. As atomic mass, 185, is the sum of protons and neutrons, number of neutrons is:

185 - 75 = 110 neutrons

Thus, right answer is:

d. 75 protons, 110 neutrons