Which statement is true regarding isotopes?

Isotopes are variations of the same chemical element that have the same number of protons but differ in the number of neutrons. This difference in neutron count alters the atomic mass of each isotope of that element, leading to distinct isotopes with varying physical properties, such as stability and radioactivity.

Because isotopes maintain the same number of protons, they retain the same chemical properties. However, the change in the number of neutrons is what defines them as different isotopes of the same element. For example, carbon-12 and carbon-14 are both isotopes of carbon; carbon-12 has six neutrons, while carbon-14 has eight.

The other statements do not accurately describe isotopes. The atomic mass for all isotopes cannot be the same since it directly depends on the number of neutrons. Additionally, isotopes do not have the same number of neutrons, which is fundamental to their definition. Finally, isotopes can indeed affect atomic stability; some isotopes may be stable, while others can be unstable and radioactive.