What is true of a radioisotope that is used to date rock formations?

Answer 1

There are a number of such isotopes.

Geological dating requires isotopes with longer half lives than carbon-14 has. It also requires other things, such as that the elements involved do not wash away in water or escape as gas in an unknown manner.

What is usually done is a comparison of the amount of a radioactive element with the amount of the element it decays into. so geological dating is usually done by looking for pairs of elements bound in the rocks. These pairs include:

• samarium-147 and neodymium-143
• potassium-40 and argon-40
• rubidium-87 and strontium-87
• uranium-234 and thorium-240

There is also a dating technique in which tracks markings left by spontaneous fission of uranium are analyzed to compare quantities of uranium-235 and uranium-238.

A link to a Wikipedia article on radiometric dating is given below.

Answer 2

The half-life of all common radio-isotopes for all elements is well-known. The decay of selected elements in a substance (most commonly used is carbon) gives a good estimate of the sample's age, say to within two to five thousand years. When estimating the age of a rock sample that may be 4 billion years old, that is excellent accuracy.

Answer 3

The best known techniques to date materials use carbon isotopes, potassium isotopes, and uranium isotopes. This is called radiometric dating.

Answer 4

Uranium-238 is one radioisotope used to date rocks.

Answer 5

parent and daughter isotopes

Answer 6

It has a long half-life

Answer 7

Carbon-14