Which symbols represent atoms that are isotopes of each other? A
and
B
and
C
and
D
and
The Correct Answer and Explanation is:
Correct Answer: C — ¹⁶O and ¹⁸O
Explanation:
To determine which pairs represent isotopes, we need to understand what isotopes are. Isotopes are atoms of the same element (same number of protons) but with different numbers of neutrons. This means they must have the same atomic number (same element) but different mass numbers (different total number of protons and neutrons).
Let’s evaluate each option:
A. ¹⁴C and ¹⁴N
- ¹⁴C has 6 protons (carbon), and ¹⁴N has 7 protons (nitrogen).
- Different elements → Not isotopes
B. ¹³¹I and ¹³¹I⁻
- Both are iodine with mass number 131.
- One is a neutral atom; the other is an ion (with one extra electron).
- Same number of protons and neutrons → Same isotope
- But this is not a pair of different isotopes — they are the same isotope in different ionic forms → Not correct
C. ¹⁶O and ¹⁸O
- Both are oxygen atoms (8 protons), but have different mass numbers: 16 and 18.
- This means ¹⁶O has 8 neutrons and ¹⁸O has 10 neutrons.
- Same element, different number of neutrons → They are isotopes of each other
- ✅ Correct
D. ²²²Rn and ²²²Ra
- ²²²Rn (radon) has 86 protons; ²²²Ra (radium) has 88 protons.
- Different elements → Not isotopes
Conclusion:
Option C (¹⁶O and ¹⁸O) is correct because these are atoms of the same element (oxygen) with different numbers of neutrons, which is the definition of isotopes. This distinction is important in nuclear chemistry, medicine, and environmental science, where different isotopes behave the same chemically but can differ in stability and radioactivity.
