How radioactive dating works chemically

In an hourglass, grains of fine sand fall at a steady rate from the top bowl to the bottom.

After one hour, all the sand has fallen into the bottom bowl.

He walks into the room when half the sand is in the top bowl, and half the sand is in the bottom bowl.

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It is the interpretation of these chemical analyses that raises potential problems.

To understand how geologists “read” the age of a rock from these chemical analyses, let’s use the analogy of an hourglass “clock” (Figure 2).

Some isotopes are radioactive; that is, they are unstable because their nuclei are too large.

To achieve stability, the atom must make adjustments, particularly in its nucleus.

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.Specially equipped laboratories can do this with accuracy and precision.So, in general, few people quarrel with the resulting chemical analyses.Each atom is thought to be made up of three basic parts.The nucleus contains protons (tiny particles each with a single positive electric charge) and neutrons (particles without any electric charge).Examples are granites (formed by cooling under the ground) and basalts (formed by cooling of lava at the earth’s surface).

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