Which of the following best describes the radioactive decay of carbon-14 to nitrogen-14? A) Fusion, B) Precipitation, C) Nuclear transformation, D) Combustion, or E) Reduction.
There’s quite a big clue to the right answer in the question. Radioactive decays always involve the nucleus in some way. An atom of carbon-14 will have electrons surrounding a nucleus. Carbon has an atomic number of six. So any nucleus of carbon must have six protons. The mass number of carbon-14 is obviously 14. So we have eight neutrons in the nucleus of a carbon-14 atom. That’s 14 minus six. In this mysterious radioactive decay process, we’ve converted carbon-14 into nitrogen-14. The atomic number of nitrogen is seven. So we have seven protons in the nucleus. But the mass number hasn’t changed. So we now have seven neutrons instead of eight.
So the conversion of carbon-14 to nitrogen-14 means that we are gaining a proton and losing a neutron. This can be explained if the radioactive decay involves a neutron turning into a proton. This is exactly what happens during beta decay. A neutron in the nucleus decays into a proton, releasing a beta particle among other things. A beta particle is simply a high-energy electron. This electron doesn’t come from the surrounding cloud. So if we were being precise, we would show a positive charge on the nitrogen. However, charges are normally left out for equations of nuclear decay processes.
Now that we’ve had a look at what’s exactly going on in this process, let’s look at the five options and see which one best describes the radioactive decay of carbon-14 to nitrogen-14.
Fusion, as in nuclear fusion, involves nuclei combining together. The most popular example in the universe is the thermonuclear process going on in the sun. Where hydrogen nuclei fuse together to form helium nuclei. However, we’re only dealing with one nucleus transforming into another nucleus. So this is not a correct answer.
A precipitation reaction is one where we produce a solid from solution. A good example though of precipitation is when we mix lead nitrate solution with potassium iodide solution, forming led iodide and potassium nitrate. The lead iodide precipitates as a beautiful crystalline yellow solid. However, the conversion of carbon-14 to nitrogen-14 is not an example of a precipitation.
On the other hand, nuclear transformation is an excellent description of the process whereby carbon-14 is transformed into nitrogen-14. There are radical changes in the identity of particles that make up the nucleus and vast amount of energy released. However, we should be careful. The question says we’re looking for the best description, not just an adequate one. So let’s have a look at the other two to see if they improve on nuclear transformation.
Combustion is the reaction with oxygen. For instance, the complete combustion of methane involves one molecule of methane reacting with two molecules of oxygen, producing carbon dioxide and two molecules of water. There’s no sign of oxygen in the process of transforming carbon-14 to nitrogen-14. So combustion is not an answer.
Reduction is generally a term reserved for chemical reactions in which we see a reduction in the oxidation state of one species or another or a gain of electrons. However, we don’t tend to talk about reduction or oxidation when dealing with purely nuclear reactions. We generally need the identity of the elements to stay the same in order to compare their oxidation states.
However, if you wanted to, you could see that we’re transforming from an oxidation state of zero to an oxidation state of positive one, which is the opposite of a reduction. However, this would not be the best way to eliminate reduction as an option. However, whichever way you look at it, the best way to describe radioactive decay of carbon-14 to nitrogen-14, out of these options, is nuclear transformation.