Why is it impossible to predict when an individual unstable nucleus will decay?

It is impossible to predict when an individual unstable nucleus will decay because radioactive decay is a random process. Each nucleus has a certain probability of decaying over a given time period, but the exact moment of decay cannot be determined.

This answer effectively explains the randomness of radioactive decay, which is crucial for understanding the nature of nuclear processes. The question tests the student's understanding of the concept of randomness in radioactive decay.