With reference to 'Isotopes', which of the following statements is/are correct?

Question

With reference to 'Isotopes', which of the following statements is/are correct?

1. Atoms with identical atomic numbers but different atomic mass numbers are known as isotopes.

2. Protium, Deuterium and Tritium are isotopes of carbon.

Select the correct answer from the code given below:

1. A. Only 2
2. B. Neither 1 nor 2
3. C. Both 1 and 2
4. D. Only 1 (Correct answer)

Correct Answer

Option D — Only 1

Detailed Solution & Explanation

The correct answer is Only 1.

Key Points

• Statement 1 is correct. Isotopes are atoms of the same element having the same atomic number (same number of protons) but different mass numbers (different numbers of neutrons).
• Statement 2 is incorrect. Protium, Deuterium and Tritium are isotopes of HYDROGEN, not carbon.
• Only statement 1 holds, giving option (d).

Additional Information

• The three isotopes of hydrogen: Protium (¹H) with no neutron, Deuterium (²H or D) with one, and Tritium (³H or T) with two. Only tritium is radioactive. Heavy water (D₂O) is used as a moderator in nuclear reactors, including India's PHWRs.
• Carbon's isotopes are C-12 (the standard for atomic mass), C-13 and the radioactive C-14, used in radiocarbon dating of organic remains up to roughly 50,000 years old.
• Keep the related terms distinct:
  • Isotopes — same atomic number, different mass number (same element)
  • Isobars — same mass number, different atomic number (different elements)
  • Isotones — same number of neutrons
• Useful radioisotopes: Cobalt-60 in cancer therapy, Iodine-131 for the thyroid, Uranium-235 as reactor fuel, and Phosphorus-32 in agricultural research.