Probabilities are used in the quantum mechanical model of the atom because of heisenberg's uncertainty principle. this principle states that the and of an electron can be measured, but not simultaneously.

Position and momentum

Explanation:

The Heisenberg uncertainty principle also called the uncertainty principle states that the position and momentum of a particular particle cannot be measured with precision at the same time.

It means that to determine either of the two properties, we have to do that at a later time and not at the same time. Doing both at the same time will not yield a correct value for the two.

The theory was put forward by a German physicist by the name Werner Heisenberg in the year 1927.

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.

that's what i got you can count the number of atoms