If another 4.5 billion years were to pass, then half of the remaining half of uranium-238 would also decay, leaving 25% uranium to 75% lead.
If a scientist were to compute this, he or she would say two half-lives went by at a rate of 4.5 billion years per half-life; therefore, the sample is approximately 2 times 4.5 billion, or 9 billion years old. So you see, earth scientists are able to use the half-lives of isotopes to date materials back to thousands, millions, and even to billions of years old.
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So, to sum this all up, radioactive dating is the process scientists use to conclude the ages of substances dating back several to many years ago by using the isotopes of elements and their half-lives.An isotope is a variation of an element based upon the number of neutrons.The disintegration of the neutrons within the atom of the element's nucleus is what scientists call radioactivity.An isotope disintegrates at a constant rate called the half-life, or the time it takes for half the atoms of a sample to decay. By counting the number of half-lives and the percentages remaining of parent and daughter isotopes, scientists are able to determine what they call the absolute age of a discovery.Carbon, uranium, and potassium are just a few examples of elements used in radioactive dating.
Each element is made up of atoms, and within each atom is a central particle called a nucleus.Radioactive dating uses the ratios of isotopes and their specific decay products to determine the ages of rocks, fossils, and other substances.Elements occur naturally in the earth, and they can tell us a lot about its past.They then count the number of half-lives passed and compute the absolute age of the sample.Absolute age is just a fancy way of saying definitive or specific age as opposed to the relative age, which only refers to how old or young a substance is in comparison to something else.Carbon-14 has a half-life of approximately 5,730 years and produces the decay product nitrogen-14.