What role do neutrons play in isotopes?

Neutrons determine the isotope of an element by varying the atomic mass without changing the atomic number.

Isotopes are variants of a particular chemical element which, while having the same number of protons and electrons, have different numbers of neutrons. This means that they have the same atomic number (which defines the element), but different atomic masses. The atomic number is the number of protons in an atom's nucleus, and the atomic mass is the sum of the protons and neutrons. Therefore, the number of neutrons in an atom determines its isotope.

For example, hydrogen, the first element on the periodic table, has three isotopes: protium, deuterium, and tritium. All three isotopes have one proton, but protium has no neutrons, deuterium has one neutron, and tritium has two neutrons. Despite these differences, all three isotopes are still hydrogen because they have the same atomic number.

Neutrons play a crucial role in the stability of the nucleus. The strong nuclear force binds protons and neutrons together in the nucleus, overcoming the repulsion between protons. However, if there are too many or too few neutrons, the nucleus can become unstable and undergo radioactive decay. This is why isotopes with different numbers of neutrons can exhibit different levels of radioactivity.

In summary, neutrons play a vital role in isotopes. They determine the atomic mass of an atom without changing its atomic number, thus defining the isotope of the element. They also contribute to the stability of the atom's nucleus, with variations in neutron number leading to differences in nuclear stability and radioactivity.