Short notes on radiocarbon dating
Some of the atoms eventually change from one element to another by a process called radioactive decay.
Further evidence comes from the complete agreement between radiometric dates and other dating methods such as counting tree rings or glacier ice core layers.
Similarly, when all the atoms of the radioactive element are gone, the rock will no longer keep time (unless it receives a new batch of radioactive atoms).
The rate of loss of sand from from the top of an hourglass compared to exponential type of decay of radioactive elements.
Most processes that we are familiar with are like sand in an hourglass.
In exponential decay the amount of material decreases by half during each half-life.
You cannot predict exactly when any one particular grain will get to the bottom, but you can predict from one time to the next how long the whole pile of sand takes to fall.