I don't know if there is a "solid and correct" answer to this because both questions are open to debate. It is never easy to know who first discovered something. If you look at the first link, you can see that many different people are credited with discovering this law.
As far as who is the first modern scientist, that's even harder. There are two problems. First, you have to define what you mean by "modern scientist?" Is it someone who uses the scientific method? Second, we cannot possibly know who first did that (or whatever else you would say makes someone a modern scientist.). The usual answers for who the first modern scientist was are Galileo or Newton, but it really can't be proved.