Final answer:
The isotope carbon-14 contains 6 protons in its nucleus. Organisms predominantly use the stable isotope carbon-12 to synthesize molecules like glucose. Carbon-14's radioactivity makes it useful for carbon dating in archaeological studies.
Step-by-step explanation:
The element carbon (C) has an atomic number of 6, which means that all neutral carbon atoms contain 6 protons in their nucleus, regardless of the isotope. In the case of the isotope carbon-14 (14C), it also contains eight neutrons in the nucleus, in addition to the six protons. The six protons define the element as carbon, and it is the number of neutrons that differ among isotopes, carbon-12 having six neutrons, carbon-13 having seven, and carbon-14 having eight.
Since every atom of carbon has six protons, the isotope carbon-14 has six protons just like carbon-12 and carbon-13. The difference lies in the number of neutrons and this results in different physical properties, such as radioactivity in the case of carbon-14. In biological systems, organisms are more likely to utilize carbon-12 for synthesizing molecules like glucose (C6H12O6) because it is stable and does not emit radiation.
Carbon-14 is used in an important method called carbon-14 dating, which relies on its radioactive decay to determine the age of organic materials. This is because when an organism dies, its intake of carbon-14 ceases and the existing carbon-14 begins to decay, with a half-life of 5730 years.