Log in to Teachers' Domain to download, share, rate, save, and match to state standards. All living things contain carbon. Isotopes are variations of an element; the number of protons in each isotope is the same, but the number of neutrons differs. Carbon has three natural isotopes: Carbon is a rare version of carbon with eight neutrons. It is radioactive and decays over time.
When carbon decays, a neutron turns into a proton and it loses an electron to become nitrogen The length of time it will take for half the amount of carbon to decay is known as its half-life.
Here's additional information not featured in this video that can be shared with students: Carbon dating measures the ratio of carbon to carbon and uses the known half-life of carbon to estimate the age of organic material. Questions for Discussion What is the most common form of carbon? How is carbon different? What does it mean to say that an isotope is unstable? Describe the radioactive decay of carbon How does the scientist in the video use carbon to help study changes in climate?
Scientists now know that most elements come in more than one version. The different versions are called isotopes. Consider carbon, the backbone of life. It has three natural isotopes, or versions. Each has six protons and six electrons. That's what makes them all carbon.
The difference between them is the number of neutrons in the nucleus. Neutrons are electrically neutral particles that act as glue to hold atoms together. What we think of as normal carbon is called carbon But about one percent of carbon atoms have an extra neutron, giving them seven.
And about one in a million have eight neutrons. And that rare version of carbon has proven to be a crucial tool for unlocking the past. So this, then, is Mono Lake. Right here, at the foot of the Sierra Nevada. He's studying the long history of droughts in California, trying to determine how frequently they occur and how long they last.
Over the millennia, the water level has risen and fallen, as the area has cycled between wet periods and dry times. So that sandy area should be the level? During times when the climate was dry, Mono Lake dropped down, exposed the shore lands, and allowed trees and shrubs to grow. When the dry periods ended and the water level rose, the trees drowned, marking the end of the droughts. Since then, the remains of those trees have been well preserved by the arid climate. These droughts were long and persistent.
To determine how long ago these droughts occurred, Scott is using carbon to date the trees. Unlike the other natural isotopes of carbon, carbon is unstable. Over time, its atoms begin to deteriorate. One of its neutrons turns into a proton and spits out an electron.
Now, with seven protons instead of six, it's turned into nitrogen. That process is called radioactive decay. And scientists know exactly how long it will take for half of any amount of carbon to decay away. Scientists call that time its "half-life. The amount of carbon stays the same, but the carbon decays away, at a constant rate, making carbon a ticking atomic clock.