Isotopes are atoms of elements which have _____.

Isotopes are indeed defined as atoms of the same element that share the same atomic number, meaning they have the same number of protons in their nuclei, but differ in their atomic weights due to variations in the number of neutrons. This characteristic allows isotopes of an element to exhibit similar chemical properties while having different physical properties, such as stability and radioactive decay rates.

The distinction between isotopes is crucial in various fields, including medicine, archaeology, and nuclear energy, as different isotopes can have diverse applications based on their stability and behavior. For example, carbon-12 and carbon-14 are isotopes of carbon; they both have six protons (same atomic number) but differ in the number of neutrons, resulting in different atomic weights.

The other options do not accurately represent the definition of isotopes, as they either confuse the relationship between atomic number and atomic weight or describe configurations that do not pertain to isotopic variation. Understanding isotopes is fundamental for comprehending concepts in chemistry and physics, and their applications highlight the significance of atomic structure in scientific inquiry.