Final Answer:
Mass number determines if something is an isotope. So, Option B is correct.
Step-by-step explanation:
Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons in their nuclei. The key factor determining if something is an isotope is the mass number. The mass number is the sum of protons and neutrons in an atomic nucleus.
While the atomic number (option a) represents the number of protons, it doesn't account for the variations in the number of neutrons. Isotopes share the same atomic number but have different mass numbers, distinguishing them from each other.
Isotopes play a crucial role in biology, particularly in radiometric dating and medical applications. In radiometric dating, the decay of isotopes is used to estimate the age of fossils and geological formations. For example, carbon-14 dating relies on the decay of the isotope carbon-14 to estimate the age of organic materials.
In medicine, isotopes are utilized in techniques like positron emission tomography (PET) scans, where radioactive isotopes are introduced into the body to track and visualize biological processes. The specific isotope used and its properties determine the application, emphasizing the importance of understanding isotopes in various biological contexts.
Understanding isotopes is essential for comprehending the behavior of elements in biological systems. Different isotopes of an element may exhibit distinct physical and chemical properties due to variations in atomic mass. This knowledge is fundamental in fields like biochemistry and molecular biology, where isotopic labeling is employed to trace the movement of specific atoms in molecules.
In conclusion, the mass number is the critical factor that defines isotopes, and this understanding forms the basis for their diverse applications in biological research and medical diagnostics.