How do I randomize points within a certain area using Processing.?

Okay, so I have to do this project for my Computer Science class, and we are doing random() in Processing. What I want to do is to create an atom-like structure by putting a little circle at the center (nucleus) of the page, and to make two bigger circles around it, in which the area between them is where electrons would be randomized. I attached a terrible looking picture to roughly estimate what I'd like it to look like. As you can see, the nucleus is in the center, and then there are two circles. All of the area between those circles I would like to have a point randomly popping into that area using the random function.

The only thing I could possibly think of is using equations of circles, maybe inequalities, to set the parameters.

Anything would be appreciated, because I'm beat. I have no idea how to go about this.