A radioactive isotope of carbon, 14C, undergoes beta decay to form an unknown isotope X. Which of the following is the correct identity of isotope X?

• A. 14O
• B. 13C
• C. 12C
• D. 14N

Answer: (D)

Verified step by step guidance

1. Understand the process of beta decay: in beta decay, a neutron in the nucleus is converted into a proton, and a beta particle (an electron) is emitted.
2. Recognize that during beta decay, the atomic number (number of protons) increases by 1, while the mass number (total number of protons and neutrons) remains the same.
3. Identify the original isotope: carbon-14 has an atomic number of 6 (since carbon's atomic number is 6) and a mass number of 14.
4. Apply the change in atomic number due to beta decay: increase the atomic number by 1, so the new atomic number is 7, but the mass number stays 14.
5. Determine the element with atomic number 7 and mass number 14: atomic number 7 corresponds to nitrogen, so the new isotope is nitrogen-14 (\$^{14}N\$).