Potassium 40 dating 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.
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 are the moving particles which constitute the radioactivity measured by Geiger counters and the like.) The end result is stable atoms, but of a numbers of protons and electrons.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.These parent radioisotopes change into daughter lead-206, lead-207, argon-40, strontium-87, and neodymium-143 isotopes, respectively.Thus, geologists refer to uranium-lead (two versions), potassium-argon, rubidium-strontium, or samarium-neodymium dates for rocks.However, while the number of neutrons varies, every atom of any chemical element always has the same number of protons and electrons.
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.
Note that the carbon-14 (or radiocarbon) method is not used to date rocks, because most rocks do not contain carbon.
Unlike radiocarbon (Sm)—are not being formed today within the earth, as far as we know.
Thus, the parent isotopes that decay are called radioisotopes.
Actually, it isn’t really a decay process in the normal sense of the word, like the decay of fruit.
The nucleus contains protons (tiny particles each with a single positive electric charge) and neutrons (particles without any electric charge).