Radioactive dating rock

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So, for example, every carbon atom contains six protons and six electrons, but the number of neutrons in each nucleus can be six, seven, or even eight.

Therefore, carbon has three isotopes, which are specified as carbon-12, carbon-13 and carbon-14 (figure 1). Comparison of stable and unstable atoms of the element carbon.

This process of changing the isotope of one element (designated as the parent) into the isotope of another element (referred to as the daughter) is called radioactive decay.

Thus, the parent isotopes that decay are called radioisotopes.

Geologists regularly use five parent isotopes as the basis for the radioactive methods to date rocks: uranium-238, uranium-235, potassium-40, rubidium-87, and samarium-147.

These parent radioisotopes change into daughter lead-206, lead-207, argon-40, strontium-87, and neodymium-143 isotopes, respectively.

Because of the short length of the carbon-14 half-life, carbon dating is only accurate for items that are thousands to tens of thousands of years old. Geologists must therefore use elements with longer half-lives.

For instance, potassium-40 decaying to argon has a half-life of 1.26 billion years and beryllium-10 decaying to boron has a half-life of 1.52 million years.

Similarly, 11460 years after an organism dies, only one quarter of its original carbon-14 atoms are still around.They have six protons in their nuclei and six electrons orbiting their nuclei, which gives carbon its chemical properties.It is the number of neutrons in their nuclei that varies, but too many neutrons make the nuclei unstable, as in carbon-14.Geologists measure the abundance of these radioisotopes instead to date rocks.Most people today think that geologists have proven the earth and its rocks to be billions of years old by their use of the radioactive dating methods. Given so much time, the ‘impossible’ becomes possible, the possible probable, and the probable virtually certain.

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