Interesting brain snack.
In the first train of thoughts someone assumed that thoughts are a chemical reaction. I think this is not necessarily true nor can be approved. In the second train, if we can’t decide which atom will decay and when, it does not mean it is random either. And by naming things and phenomena some fancy names does not make it real or true, The way modern physicists are doing, like dark matter and dark energy ( the new age "Aether").
To stay within the subject, my opinion is: nothing is random, everything in the universe happened according to the will of the smart universe and human free will which is unpredictable 100%.