______ are atoms having the same mass number but different atomic numbers?

Appeared in: RRB Nsg. Superintendent-20 July 2019 (Shift-2)

Explanation

The question asks for the term describing atoms with the same mass number but different atomic numbers.
This is the exact definition of isobars.
The word 'isobar' combines 'iso' (equal) and 'bar' (weight/mass), referring to their equal mass number.
An example is Carbon-14 and Nitrogen-14. Both have a mass number of 14, but their atomic numbers (6 and 7, respectively) are different, making them different elements.

Option A: Isotopes have the same atomic number but different mass numbers, which is the opposite of the definition given in the question.
Option C: Isomers relate to the arrangement of atoms within a molecule (chemical isomers) or the energy state of a nucleus (nuclear isomers), not the fundamental count of protons and neutrons that defines isobars.
Option D: Isohyets are completely unrelated to atomic structure. It is a term from geography for lines of equal rainfall on a map.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Definitions of Isobars, Isotopes, and Isomers in chemistry as background academic context rather than a clinical decision trigger.
Understanding the difference between isotopes and isobars is fundamental to nuclear medicine.
Radioisotopes (unstable isotopes) are crucial for diagnostics and therapeutics. For example, Technetium-99m is used for imaging, and Iodine-131 is used for treating thyroid disorders. These are chosen for their specific decay properties, not because they are isobars.
What if the question was about medical imaging? The answer would likely involve a specific radioisotope, such as Technetium-99m for SPECT scans or Fluorine-18 (in FDG) for PET scans, highlighting the importance of isotopes, not isobars, in clinical practice.

How to Approach the Question

This is a factual recall question based on a definition.
First, identify the key defining characteristics in the question: 'same mass number' and 'different atomic numbers'.
Break down the prefixes of the options. 'Iso-' means 'same'.
'Topes' (from 'topos' for place) refers to the same place in the periodic table (same atomic number).
'Bars' (from 'baros' for weight) refers to the same weight (same mass number).
Match the question's definition (same mass/weight) to the correct term, 'isobars'.

Concept Tested & Keywords

QntYx8Q3eXNqEpYYQm4aI_

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart B (pp 240-463 of 478) pp. 175-177, 176-178

Practise the full RRB Nsg. Superintendent-20 July 2019 (Shift-2)

Attempt every question from this paper in a timed mock, then review the full solution for each one.