Radioactive decay

[z3ro]

I was taught that radioactive decay is a COMPLETELY random process... but I can't figure out why   
It is really random? completely unpredictable?     

[Axon]

I was taught that radioactive decay is a COMPLETELY random process... but I can't figure out why   
It is really random? completely unpredictable?     

I don't know what do you mean by random process? Radioactive decay happens when atoms have excess energy, and since all atoms in the universe always tend to become in a stable state. Therefore, the atoms with excess energy(excited state) lose this energy in the form of radiation called radioactive decay.

[z3ro]

Radioactive decay is a stochastic (i.e., random) process at the level of single atoms, in that, according to quantum theory, it is impossible to predict when a particular atom will decay. However, the chance that a given atom will decay is constant over time.