Question

Q1. Carbon-14 – or 14C – is a radioactive isotope of carbon with a half-life of 5,730 years. It decays into nitrogen-14 – or 14N – , which is a stable isotope of nitrogen.
(a) Which of the three nuclear decay processes describes the decay? Explain. (Hint: You can get the atomic number of carbon and nitrogen from a periodic table.)
(b) Write down the equation for the decay.
(c) What is the decay constant for 14C?
All isotopes of carbon can be found in any living organism. The carbon is taken up by eating and breathing. After the organism dies no more carbon will be replenished and 14C still decays. By measuring the remaining 14C, when the organism died can be determined.
(d) An archaeologist has found bones from an animal that have 30% of 14C compared to its living form. How old is the animal body?
(e) What would be the percentage of 14C if the animal body was 25,000 years old?
(f) This method of radiocarbon dating can only be used for relatively young fossils (up to 50,000 years old). Why is that?

Answer 1