What are isotopes? A.) Atoms of the same element that have a different number of protons
B.) Atoms of the same element that have a different number of neutrons
C.) Atoms of different elements that have the same number of neutrons
D.) Atoms that are unstable

B. ATOMS OF THE SAME ELEMENT THAT HAVE A DIFFERENT NUMBER OF NUETRONS

Explanation:

Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.