Question

Which of the following are isobars?

• A. $^{232}_{92}U$ and $^{238}_{92}U$
• B. $^2_1H$ and $^3_1H$
• C. $^3_1H$ and $^3_2He$
• D. $^{14}_7N$ and $^{15}_7N$

Hint:

Remember the definitions: Isotopes have the same atomic number ($Z$), Isobars have the same mass number ($A$), and Isotones have the same number of neutrons ($A-Z$).

Answer 1

The Correct Option is C

Step 1: Isobars are atoms having same mass number ($A$) but different atomic numbers ($Z$).
Step 2: Checking each option:
(1) Same $Z$, different $A$ → Isotopes.
(2) Same $Z$, different $A$ → Isotopes.
(3) $^3_1H$ and $^3_2He$: Same $A=3$, different $Z$ → Isobars.
(4) Same $Z$, different $A$ → Isotopes.
Hence, correct answer is option (3).