Final answer:
Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons, resulting in different mass numbers while retaining identical chemical properties. For example, the isotopes of hydrogen, such as protium, deuterium, and tritium, differ only in their number of neutrons and atomic mass.
Step-by-step explanation:
Atoms of an element that contain different numbers of neutrons are called isotopes. Each isotope of a given element has the same atomic number but a different mass number (A), which is the sum of the numbers of protons and neutrons. For instance, all carbon atoms contain six protons (atomic number = 6), but isotopes of carbon can have six, seven, or eight neutrons, leading to mass numbers of 12, 13, or 14 respectively.
Although isotopes have different mass numbers, they exhibit identical chemical properties because they have the same number of protons and electrons. The main difference between isotopes of the same element is their atomic mass. Nuclear scientists can differentiate and separate different isotopes, while in a chemical laboratory, they often appear and react the same, making them difficult to distinguish without sophisticated technology.
Examples of isotopes include hydrogen's forms: protium with no neutrons, deuterium with one neutron, and tritium with two neutrons. Despite these differences in neutrons, all forms have one proton, characterizing them as hydrogen, and they differ only by their mass number, not their chemical behavior.