Video Transcript
The radioactive decay curve of fermium-253 is shown on the graph. What is the half-life of fermium-253?
The half-life is the amount of time required for one-half of the radioactive nuclei in a sample to decay. A radioactive nucleus is unstable. It will undergo radioactive decay to become stable. Radioactive decay is a naturally occurring process, where radiation, in the form of energy or particles, is emitted from the nucleus. The radioactive isotope in this question is fermium-253. Fermium-253 is a synthetic element, meaning it’s always made in a lab and does not occur naturally. All atoms of fermium are radioactive.
Let’s take a look at the radioactive decay curve that we’ve been given in this question. On the 𝑦-axis, we have the percentage of fermium that is remaining in the sample. On the 𝑥-axis is the time in days. We need to figure out the half-life of fermium-253 using this graph. Remember that after one half-life, half of the fermium-253 in the sample will decay.
When we start off, we can see that 100 percent of the sample is made of fermium-253. After one half-life, only 50 percent of the fermium-253 will still be remaining. If we use the graph to see how many days have passed, we’ll see that it took three days for 50 percent of the fermium-253 to decay. So the half-life of fermium-253 is three days. So, if we start off with 100 grams of fermium-253, after three days, half of the fermium-253 would have decayed into a stable isotope. This means that only 50 grams of the sample is now fermium-253. After another half-life or another three days, another 50 percent of the fermium-253 will have decayed. This means that only 25 percent of the sample is now fermium-253.
So, by inspecting the radioactive decay curve of fermium-253, we identified that the half-life of fermium-253 is three days.
