This means that after approximately 4.5 billion years, half of an original sample containing this isotope will decay into its decay product, forming the new isotope, Pb 206 (lead 206).
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.
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 --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-14 is a specific isotope used in dating materials that were once living.
The half-life is so predictable that it is also referred to as an atomic clock.
Can you guess how much uranium-238 would remain after the passing of another half-life?
(Remember, isotopes are variations of elements with a different number of neutrons.) The half-life is reliable in dating artifacts because it is not affected by environmental or chemical factors; it does not change.
Within the nucleus, we find neutrons and protons; but for now, let's just focus on the neutrons.
These neutrons can become unstable, and when they do, they release energy and undergo decay. Radioactivity occurs when the nucleus contains an excess amount of neutrons.
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 our Earth's past.