Nuclides with the same atomic number Z (i.e., the same element) but different mass numbers are termed what in nuclear chemistry?

Introduction / Context:
Precise nuclear vocabulary enables clear communication about nuclides. When two atoms share the same atomic number Z, they are the same chemical element; if their mass numbers A differ, we call them isotopes. This is central to explaining fractional atomic weights and why natural samples of an element often contain multiple isotopes in fixed proportions.

Given Data / Assumptions:

• Z is identical for the nuclides being compared.
• Mass numbers differ due to different neutron counts.
• Chemical behavior is largely the same because electron configuration depends on Z.

Concept / Approach:
Definitions: isotopes (same Z, different N and thus different A); isobars (same A, different Z); isotones (same N, different Z); isomers (same Z and A, different nuclear energy states). The stem specifies “same atomic number,” which immediately maps to isotopes.

Step-by-Step Solution:
Recognize that Z determines the element.Different A means neutron counts differ.Same Z + different A → isotopes by definition.

Verification / Alternative check:
Classic examples include chlorine-35 and chlorine-37, carbon-12 and carbon-13, and uranium-235 and uranium-238. Each pair shares Z but has a different A, matching the concept of isotopes.

Why Other Options Are Wrong:
Isobars: same A, not same Z.Isotones: same N, not same Z.Isomers: nuclear excited vs. ground state, same Z and A.Allotropes: refer to different structural forms of the same element in chemistry (e.g., graphite vs. diamond), not nuclide identity.

Common Pitfalls:
Interchanging the meanings of isobars and isotopes.Confusing nuclear terms with chemical terms like allotropy.

Final Answer:
Isotopes