Radioactivity of elements starts with an unstable elemental isotope. An unstable atom on radioactive elements carries too many protons or neutrons, and eventually, it must expel energy from the atom, and become an entirely new stable element through the process of beta decay. This process, for every unstable atom, is completely spontaneous and there is no specific timeline. But in a large group of these radioactive isotopes, scientists have found statistical averages for these element’s half-lives, or the average time required for half of the radioactive isotopes in a sample to decay. From this 50 percent mark, the process starts over, and it will take approximately the same amount of time for the 50 percent of leftover radioactive isotopes to decay. The discovery of radioactive half-lives has led to the discovery of Earth’s age.
The timelines of radioactive half-lives vary greatly between elements. Carbon-14, for example, has a half-life of 5,730 years. It is great for short term dating accuracy, as the percentage of Carbon-14 molecules will tell you how many half-lives the objects has lived. But at around 57,000 years, basically all of the Carbon-14 molecules have transformed. Uranium-235, however, has a half-life of 700 million years. Scientists have found large clusters of this isotope in the Earth’s oldest meteorites, and based on the unstable uranium’s half-live, and the concentration of the decayed elements surrounding it, scientists have dated the oldest existing rocks on Earth to about 4.3 billion years old.
This is just one of so many examples showing us how creative scientists can be in their quest for new information!
Astronomy 