Two atoms are isotopes of the same element. Which of the following should
be different for these two atoms?
A. The behavior in a chemical reaction
B. The number of neutrons
C. The type of element
D. The number of protons
Isotopes are atoms with different atomic masses which have the same atomic number. The atoms of different isotopes are atoms of the same chemical element; they differ in the number of neutrons in the nucleus.
