Why are Carbon-14 and carbon-12 considered to be isotopes?
A. Carbon-14 decays at a faster rate that Carbon-12
B. Carbon-14 is more stable than Carbon-12.
C. Carbon-14 has more neutrons than carbon-12.
D. Carbon-13 is roughly 2 any heavier than Carbon-14.
E. Both atoms have six protons in the nucleus, but have different atomic masses.
The Correct Answer and Explanation is:
The correct answer is C. Carbon-14 has more neutrons than Carbon-12.
Explanation:
Carbon-14 and Carbon-12 are considered isotopes of the element carbon because they both have the same number of protons but differ in the number of neutrons they contain. Isotopes are variants of the same element that have the same atomic number (the number of protons), but a different atomic mass due to the differing number of neutrons.
- Carbon-12 has 6 protons and 6 neutrons, making its atomic mass 12 (6 protons + 6 neutrons).
- Carbon-14 also has 6 protons, but it contains 8 neutrons (6 protons + 8 neutrons), giving it an atomic mass of 14.
This difference in the number of neutrons is what makes them isotopes. Both carbon isotopes share chemical properties because they have the same number of electrons (and thus the same electron configuration), but their physical properties, such as atomic mass, differ due to the neutron count.
Why the other options are incorrect:
- A. Carbon-14 decays at a faster rate than Carbon-12: This is incorrect. Carbon-14 undergoes radioactive decay over time (through beta decay) and has a half-life of about 5,730 years. Carbon-12, however, is stable and does not undergo any decay. The decay rate is related to the stability of the isotope, but this is not why they are considered isotopes.
- B. Carbon-14 is more stable than Carbon-12: This is incorrect. Carbon-14 is actually radioactive and unstable, whereas Carbon-12 is stable. Stability or instability is not what defines an isotope.
- D. Carbon-13 is roughly 2 amu heavier than Carbon-14: This is incorrect. Carbon-13 is actually lighter than Carbon-14, not heavier. Carbon-13 has 7 neutrons, while Carbon-14 has 8 neutrons.
- E. Both atoms have six protons in the nucleus, but have different atomic masses: While this statement is true, it is not specific enough to explain why they are isotopes. The key difference is the number of neutrons, not just the atomic mass. Thus, option C provides a clearer and more accurate explanation.
In summary, Carbon-14 and Carbon-12 are isotopes because they have the same number of protons but different numbers of neutrons, which results in different atomic masses.